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A Systematic Review of Sleep Deprivation and Neurobehavioral Function in Young Adults

Stephanie griggs.

Case Western Reserve University, Frances Payne Bolton School of Nursing, Cleveland, Ohio, USA 44106

Alison Harper

Case Western Reserve University, Frances Payne Bolton School of Nursing, Department of Anthropology, Cleveland, Ohio, USA 44106

Ronald L. Hickman, Jr

Ruth M. Anderson Endowed Professor of Nursing and Associate Dean for Research Case Western Reserve University, Frances Payne Bolton School of Nursing, Cleveland, OH, USA 44106

To examine the effect of sleep deprivation (total and partial) on neurobehavioral function compared to a healthy sleep opportunity (7–9 hours) in young adults 18–30 years.

Background:

More than one-third of young adults are sleep deprived, which negatively affects a range of neurobehavioral functions, including psychomotor vigilance performance (cognitive), affect, and daytime sleepiness.

A systematic review of randomized controlled trials (RCTs) on sleep deprivation and neurobehavioral function. Multiple electronic databases (Cochrane Central Registry of Controlled Trials [CENTRAL], PubMed, PsycINFO, CINAHL, and Web of Science) were searched for relevant RCTs published in English from the establishment of each database to December 31, 2020.

Nineteen RCTs were selected (N = 766, mean age = 23.7 ± 3.1 years; 44.8% female). Seven were between-person (5 were parallel-group designs and 2 had multiple arms), and 12 were within-person designs (9 were cross over and 3 used a Latin square approach). Total sleep deprivation had the strongest detrimental effect on psychomotor vigilance performance, with the largest effects on vigilance tasks in young adults in the included studies.

Conclusion:

Acute sleep deprivation degrades multiple dimensions of neurobehavioral function including psychomotor vigilance performance, affect, and daytime sleepiness in young adults. The effect of chronic sleep deprivation on the developing brain and associated neurobehavioral functions in young adults remains unclear.

1. Introduction

Sleep loss has a negative effect on multiple neurobehavioral functions, such as psychomotor vigilance performance (cognitive), daytime sleepiness, and affect ( Franzen et al., 2011 ; Van Dongen et al., 2003 ). Degradation of vigilance following sleep deprivation is one of the most robust alterations in healthy young adults aged 18–30 years ( Lim & Dinges, 2010 ). Multiple dimensions of neurobehavioral impairment are differentially affected by sleep deprivation ( Van Dongen et al., 2004 ). Sleep deprivation affects regions of the prefrontal cortex ( Chee & Choo, 2004 ), which continues to mature up to the late ‘20s ( Johnson et al., 2009 ), leading to executive dysfunctions with the prefrontal cortex ( Dinges et al., 1997 ; Nilsson et al., 2005 ). The prefrontal cortex is most vulnerable to the effects between states of sleep and wake due to the metabolic change associated with sleep deprivation ( Muzur et al., 2002 ).

Biological, social, and environmental factors converge, resulting in sleep deprivation in more than one-third (32.3%) of young adults ( Peltzer & Pengpid, 2016 ). Sleep deprivation contributes to a negative interaction between homeostatic and circadian processes. In young adulthood, there is reduced homeostatic sleep pressure (adenosine) accumulation during wakefulness, a delay in sleep timing, and a delay in releasing the onset of melatonin that peaks in the mid-’20s ( Crowley & Carskadon, 2010 ; Fischer et al., 2017 ). Motor vehicular accident risk increases at the circadian cycle nadir following total sleep deprivation which, correlates with slowing of psychomotor vigilance performance ( Patanaik, Zagorodnov, Kwoh, et al., 2014 ).

The broad effect of sleep manipulation (sleep deprivation, sleep restriction, and sleep improvement) on cognitive functioning in adolescents aged 10 – 19 years was addressed in one previous systematic review ( de Bruin et al., 2017 ). In the systematic review, the effect of total sleep deprivation was examined in 4 studies, partial sleep deprivation in 10 studies, sleep extension in one study, and cognitive behavioral therapy for insomnia in one study and 45 unique cognitive tests were reported where a vast array of cognition was assessed ( de Bruin et al., 2017 ). In the review, partial sleep deprivation had a small or no effect on cognitive functioning, total sleep deprivation negatively affected psychomotor vigilance performance, and sleep extension improved working memory in the adolescents studied ( de Bruin et al., 2017 ). However, conclusions could not be made about the specific domains affected by sleep manipulation due to the differences and quantity of tests ( de Bruin et al., 2017 ). The extent of the associations between total and partial sleep deprivation and neurobehavioral impairment (e.g., decrements in psychomotor vigilance performance – cognitive performance impairment, affect, and daytime sleepiness) remains unclear.

The primary aim of this research was to determine the effect of sleep deprivation compared to healthy sleep opportunity (sleep duration 7–9 hours) on psychomotor vigilance performance as measured by psychomotor vigilance testing (PVT) only. PVT-related outcomes may include mean and median response time, reciprocal response time slowest 10%, mean reaction time fastest 10%, number of lapses (No. of times RT is > 500 ms lapses). The secondary aim of this research was to determine the effect of sleep deprivation on affect or daytime sleepiness compared to a healthy sleep opportunity. Secondary outcomes were change in affect or daytime sleepiness outcomes measured by diagnostic criteria or self-reported questionnaires.

Our focus is on young adults aged 18 to 30 years who are at a key developmental stage at a great risk of sleep deprivation and sleep deprivation-related neurobehavioral impairment. This focus addresses a significant gap in the existing literature. Additionally, the focus on sleep deprivation with a primary outcome of psychomotor vigilance performance to assess cognitive performance via psychomotor vigilance testing, a proven assay for evaluating vigilance ( Dinges et al., 2004 ), will allow a common outcome to be synthesized across studies.

2.1. Design

The Preferred Reporting Items for Systematic Reviews and Meta-analyses Statement guidelines were followed for this systematic review ( Nagendrababu et al., 2019 ). We registered our protocol with the PROSPERO registry before implementing the search in the International Prospective Register of Systematic Reviews (Prospero; registration number CRD42021225200).

2.2. Search methods

Studies with participants between the ages of 18 to 30 years were included. Sampling adults across the lifespan has a great potential to underestimate the effects of sleep deprivation in young adults. The following studies were included in this systematic review: (1) randomized controlled trials (RCTs) of young adults published in English; (2) data collected for both the intervention and control group(s); (3) sample mean age from 18 to 30 years; and (4) one or more objectively measured neurobehavioral-related outcomes (e.g., mean reaction time, median reaction time, reciprocal response time slowest 10%, mean reaction time fastest 10%, number of lapses (No. of times RT is > 500 ms lapses) by psychomotor vigilance testing only. Additionally, affect or daytime sleepiness outcomes were also extracted if available. We excluded studies of people with: (1) known sleep disorders; (2) chronic medical; (3) severe psychiatric illness (e.g., bipolar disorder, schizophrenia); (4) Body Mass Index (BMI) > 35 kg/m 2 in addition to (5) night shift workers.

The following databases were searched with controlled vocabulary and keywords: Cochrane Central Registry of Controlled Trials (CENTRAL), PubMed, PsycINFO, CINAHL, and Web of Science. Articles published in English from the establishment of each database to December 13, 2020 were searched. We provide the PubMed search terms in Table 1 . We adjusted the syntax for the search strategies for each database as appropriate.

Database: PubMed ALL Search Strategy

The search was conducted under the guidance of a health science librarian with input from the primary and senior investigator. Also, an ancestry/bibliographic search was conducted to identify additional articles until the end of December 2020.

2.3. Search outcome

All 4,149 references were imported to Covidence ™ (Veritas Health Information) and duplicates were removed. A total of 3,110 were screened through Covidence ™ . Two reviewers independently screened all titles and abstracts with 93% agreement. Next, the two reviewers independently assessed full texts. A third reviewer resolved any disagreements regarding eligibility when consensus was not reached among the first two reviewers. The largest study was included when more than one article included the same trial and/or participants.

2.4. Quality appraisal

The risk of bias in the included studies was assessed independently by two reviewers using the Cochrane risk of bias tool through Covidence ™ ( Jørgensen et al., 2016 ). Sequence generation, concealment of allocation, blinding of outcome assessment blinding, >80% incomplete outcome data (< 80%), selective reporting of outcomes, and ‘other issues’ were the components of the risk of bias tool. The blinding domain was omitted as the intervention was sleep deprivation, and thus it would not be possible to blind participants.

2.5. Data abstraction and synthesis

A customized spreadsheet was used to extract and record data from the papers. Study characteristics, total or partial sleep deprivation with hours and length of time, age, measures used, the sample size (intervention and control groups), along with means and standard deviations of data were extracted. We contacted corresponding authors when insufficient or unclear data were reported. Extracted data were compared between the two reviewers, and disagreements were resolved by consultation with data in original papers and discussion.

We followed guidance on the conduct of a narrative synthesis described by Popay et al. (2006) . Three standardized data tables were used to organize the data which included (1) all studies, (2) between-persons designs, and (3) within-person designs. We started with a preliminary synthesis to organize findings from the studies to describe patterns along with direction and size of the effect when effects were reported. Next, we explored relationships considering factors that might explain any differences in significance or direction/size of the effect if applicable. Lastly, we assessed the robustness of the synthesis to draw conclusions and assess generalizability/reproducibility of the findings. Significant PVT outcomes and the effect size if applicable are presented in Table 2 . The between-person and within-person designs were considered and described separately as within-person comparisons have the advantage of a smaller within-person variation and possibility of a carryover effect ( Jones & Kenward, 2014 ).

Characteristics of studies

Note: ACT, actigraphy; PSG, polysomnography; TSD, total sleep deprivation; PSD, partial sleep deprivation; Lab, controlled setting; 1:1 parallel group design; multi-arm, more than two experimental conditions - only the TSD condition is listed on the table when the study has multiple arms; NR: not reported. All studies were randomized controlled trials. Data from two studies are presented in one article.

3.1. Study selection

We identified 19 RCTs and present results below. We contacted seven corresponding authors; two responded, one shared additional data, and one provided additional clarification on their data. The study selection process is illustrated in Figure 1 .

PRISMA Flow Diagram

3.2. Characteristics of the included studies

A summary of the details of the 19 RCTs included in this systematic review is presented in Table 2 . A total of 766 young adults with mean ages ranging from 20.2 to 27.5 years (mean age, 23.7 ± 3.09 years; 55.2% male) were included in these RCTs. BMI was only reported in one trial, and the mean was 20.0 ± 1.9 kg/m 2 . Seven were between-person (5 were parallel-group designs and 2 had multiple arms), and 12 were within-person designs (9 were cross over and 3 used a Latin square approach).

Sleep was measured via polysomnography in 9 studies and with actigraphy in eight studies ( Table 2 ). The setting for a majority of these studies was a controlled laboratory (e.g., temperature, sound, avoidance of alcohol and caffeine) except for four studies ( Kaida & Niki, 2014 ; Rossa et al., 2014 ; Schwarz et al., 2016 ; Schwarz et al., 2013 ). The RCTs were conducted in the following countries: the United States (8), Italy (2), Finland (1), Australia (1), Japan (1), South China (1), Singapore (2), Canada (1), and Germany (2). All RCTs had a sleep deprivation experimental condition (15 were total sleep deprivation ranging from 24 hours to 72 hours and four were partial sleep deprivation of 4-hours per night ranging from one night to four nights) and a healthy sleep opportunity (duration of 7–9 hours) comparison condition.

The dose-response effect of total and partial sleep deprivation on psychomotor vigilance performance was examined in three different RCTs ( Drake et al., 2001 ; Jewett et al., 1999 ; Van Dongen et al., 2004 ). Acute sleep deprivation was assessed in two trials ( Drake et al., 2001 ; Jewett et al., 1999 ) and chronic sleep deprivation in the other trial ( Van Dongen et al., 2004 ). All trials had one 8-hour condition and one total sleep deprivation condition, but total sleep deprivation varied in each of the trials and was for one night in one trial ( Jewett et al., 1999 ), two nights in the second trial ( Drake et al., 2001 ), and three nights in the third trial ( Van Dongen et al., 2004 ). The comparison groups also varied in dose and length with 8-hours, 5-hours, or 2-hours for one night ( Jewett et al., 1999 ); 8-hours for four nights, 6-hours for four nights, and 4-hours for two nights ( Drake et al., 2001 ); and 8-hours, 6-hours, or 4-hours per night for 14 nights ( Van Dongen et al., 2004 ).

The daytime sleepiness measures used in the trials included a 9-item self-report Karolinska Sleepiness Scale ( Akerstedt & Gillberg, 1990 ), 7-item self-report Stanford Sleepiness Scale ( Babkoff et al., 1991 ), a visual analogue scale ( Monk, 1989 ), and objective pupillography as a physiological daytime sleepiness indicator ( Lüdtke et al., 1998 ). The affect measures included the 10-item positive and negative affect schedule (PANAS) ( Watson et al., 1988 ), 100mm visual analogue profile of mood states (POMS) ( McNair et al., 1971 ), and visual analogue scale ( Tempesta et al., 2014 ).

3.3. Risk of bias

A graph summarizing the risk of bias of the included studies is presented in Table 3 and Figure 2 . We determined that a majority of the studies were of high quality, with an overall low risk of bias ( n = 8). Sequence generation was judged six times to be both low and high risk, as allocation of the participants was low risk, but the time in between the sleep deprivation trial and the control condition for cross-over studies was only a week; therefore, there was a high likelihood of carryover effects from sleep deprivation. Incomplete outcome data was unclear in 6 trials, and selective outcome reporting was unclear in one. Selective outcome reporting was determined to be both low risk and high risk as it was low risk for objective measures but high risk for self-reported measures like affect and daytime sleepiness. Other source of bias was high risk in four studies due to the trials being held outside of a controlled laboratory setting.

Cochrane Risk of Bias Assessment Across Studies (Higgins et al., 2011)

Cochrane Risk of Bias Assessment

3.4. Effect of sleep deprivation by outcome

3.4.1. effect of sleep deprivation on cognitive performance.

The effect of total sleep deprivation on cognitive performance was tested in 6 RCT’s using a between-person comparison ( n = 272); four were parallel-group ( Esposito et al., 2015 ; Franzen et al., 2008 ; Tucker et al., 2009 ; Whitney et al., 2015 ) and two had multiple-arms ( Jewett et al., 1999 ; Van Dongen et al., 2004 ). In these RCTs, the total sleep deprivation condition ranged from 24 hours to 72 hours, and all trials had a healthy sleep opportunity condition for comparison. Significant declines in psychomotor vigilance performance were observed in all trials using a between-person comparison with a slower mean reaction time in three trials ( Drake et al., 2001 ; Esposito et al., 2015 ; Tucker et al., 2009 ; Van Dongen et al., 2004 ), increased slowest 10% in one trial ( Esposito et al., 2015 ), and a higher number of lapses in four trials ( Esposito et al., 2015 ; Franzen et al., 2008 ; Haavisto et al., 2010 ; Whitney et al., 2015 ). The effect sizes ranged from small ( Franzen et al., 2008 ) to medium ( Whitney et al., 2015 ) and were not reported in four between-person comparison trials ( Esposito et al., 2015 ; Haavisto et al., 2010 ; Jewett et al., 1999 ; Tucker et al., 2009 ). In Haavisto’s trial of 20 young adults comparing 4 hours of partial sleep deprivation ( n = 13) to healthy sleep opportunity ( n = 7), lapses increased significantly for the partial sleep deprivation group compared to the healthy sleep opportunity group (0.92 ± 0.73 to 3.54 ± 0.73 vs. 0.62 ± 1.00 to 0.90 ± 1.00, p = .0321, respectively) and there was a tendency that the slowest 10% of all responses were slower in the partial sleep deprivation group, but the group difference was not significant ( p = .16) ( Haavisto et al., 2010 ).

The effect of total sleep deprivation on psychomotor vigilance performance was tested in nine RCT’s using a within-person comparison ( n = 375) ( Kaida & Niki, 2014 ; Lin et al., 2020 ; Patanaik, Zagorodnov, Kwoh, et al., 2014 ; Robillard et al., 2011 ; Rossa et al., 2014 ; Schwarz et al., 2016 ; Schwarz et al., 2013 ; Tempesta et al., 2014 ; Yeo et al., 2015 ), three of which used a Latin square approach ( Drake et al., 2001 ; Honn et al., 2020 ). Total sleep deprivation ranged from 32 to 62 hours, and the cross-over between the sleep deprivation and healthy sleep opportunity conditions ranged from one week to one month. One night of total sleep deprivation resulted in significant decrements in psychomotor vigilance performance in four of the cross-over trials ( Drake et al., 2001 ; Kaida & Niki, 2014 ; Patanaik, Zagorodnov, Kwoh, et al., 2014 ; Robillard et al., 2011 ) with a slower mean reaction time in four trials ( Adler et al., 2017 ; Drake et al., 2001 ; Kaida & Niki, 2014 ; Patanaik, Zagorodnov, Kwoh, et al., 2014 ; Robillard et al., 2011 ), slower median reaction time in two of the trials ( Kaida & Niki, 2014 ; Patanaik, Zagorodnov, Kwoh, et al., 2014 ), and a higher number of lapses in two of the trials ( Lin et al., 2020 ; Patanaik, Zagorodnov, Kwoh, et al., 2014 ).

The difference was not significant between the total sleep deprivation and healthy sleep opportunity condition in Tempesta et al. 2014 ’s cross-over trial of 25 young adults (mean age 23.8 ± 2.4 years). In this trial, a 5-minute PVT on a computer was used when a 10-minute PVT was used in most studies which may have affected these outcomes ( Tempesta et al., 2014 ). The reaction time was slower in the sleep deprivation condition in one trial; however, whether the difference between the two conditions was significant was not reported as the focus of the analysis was not on change in PVT performance ( Honn et al., 2020 ). In the cross-over trials where significant decrements in psychomotor vigilance performance from total sleep deprivation were reported, effect sizes ranged from medium ( Rossa et al., 2014 ) to large ( Lin et al., 2020 ). The effect size was not reported in four trials ( Drake et al., 2001 ; Kaida & Niki, 2014 ; Patanaik, Zagorodnov, Kwoh, et al., 2014 ; Robillard et al., 2011 ). Differences in age and sex were not discussed in all but two studies reported in one paper ( Honn et al., 2020 ), where no significant group differences in age or sex were found (p = 0.24 and 0.26 respectively).

3.4.2. Dose-response effects on cognitive performance from sleep deprivation

The dose-response effect of sleep deprivation on psychomotor vigilance performance was tested in 3 RCTs ( n = 121) ( Drake et al., 2001 ; Jewett et al., 1999 ; Van Dongen et al., 2004 ). Greater psychomotor vigilance performance impairment was observed in all three trials with larger doses of sleep deprivation ( Drake et al., 2001 ; Jewett et al., 1999 ). In Jewett’s trial of 61 young adults (0-hours, 2-hours, 5-hours, or 8-hours for one night), all PVT metrics improved as sleep duration increased ( p < .0002), particularly between the 0-hour and 2-hour sleep conditions; however, only a slight improvement was observed between the 5-hour and 8-hour sleep conditions with a 2.14-hour decay mean rate for all PVT metrics. Chronic sleep deprivation (8-hours, 6-hours, 4-hours – time in bed (TIB) per night for 14 nights) resulted in cumulative dose-dependent deficits in psychomotor vigilance performance, and daytime sleepiness showed an acute response but did not differentiate between the 6-hour and 4-hour conditions in Van Dongen’s trial of 48 young adults (mean age 26 ± 3.6 y). In this same trial, deficits in cognitive performance were equivalent between the chronic sleep deprivation of sleep to 6-hours or less per night over 10 nights and up to 2-nights of total sleep deprivation conditions ( Van Dongen et al., 2004 ). In Drake’s trial of 12 young adults using a Latin square design (no sleep loss-8 hours TIB for 4-nights; slow: 6-hours TIB hours for 4 nights; intermediate: 4-hours TIB for two nights; and rapid: 0-hours TIB for one night), higher impairment of cognitive performance impairment with rapid loss of sleep loss as opposed to when loss of sleep occurred or accumulated over time ( Drake et al., 2001 ). Also, alertness levels were lower in the 6-hour per night condition relative to the 8-hour condition in the same trial ( Drake et al., 2001 ). We present a dose response graph comparing pooled baseline to partial sleep deprivation conditions (6- and 4-hour sleep duration) and total sleep deprivation (0-hour sleep duration) mean reaction time as measured by the PVT over the days of monitoring in Figure 3 .

Dose Response graph Note: 1 day = 24 hours; 0-hour time in bed is total sleep deprivation; 4 and 6-hour time in bed is partial sleep deprivation; and 8-hour time in bed is a healthy sleep opportunity.

3.4.3. Effect of sleep deprivation on daytime sleepiness

The effect of sleep deprivation on self-reported daytime sleepiness was assessed in 5 trials ( n = 135) using a between-person comparison ( Esposito et al., 2015 ; Franzen et al., 2008 ; Haavisto et al., 2010 ; Jewett et al., 1999 ; Van Dongen et al., 2004 ) and objective daytime sleepiness was additionally assessed in one of the trials ( Franzen et al., 2008 ). Trials of total sleep deprivation ( Esposito et al., 2015 ; Franzen et al., 2008 ; Jewett et al., 1999 ; Van Dongen et al., 2004 ) and partial sleep deprivation ( Haavisto et al., 2010 ) resulted in significantly higher daytime sleepiness ratings in the sleep deprivation as opposed to the healthy sleep opportunity conditions. In comparison to the PVT, the largest magnitude of effects were seen in all measures of daytime sleepiness (2 objective and 1 self-report) in Franzen et al. 2008 ’s trial of 29 young adults following one night of total sleep deprivation ( n = 15) compared to a healthy sleep opportunity condition ( n = 14) (mean sleep latency test F = 25.08, p < .001, n 2 = 0.501, pupillary unrest test F = 11.58, p = .002, n 2 = 0.317, visual analogue scale F = 42.80, p <.001, n 2 = 0.631).

The effect of total sleep deprivation on self-reported daytime sleepiness was assessed in 4 cross-over trials ( Lin et al., 2020 ; Patanaik, Zagorodnov, Kwoh, et al., 2014 ; Tempesta et al., 2014 ; Yeo et al., 2015 ). Results were not reported in 3 trials ( Patanaik, Zagorodnov, & Kwoh, 2014 ; Tempesta et al., 2014 ; Yeo et al., 2015 ). The effect of one night of total sleep deprivation on self-reported daytime sleepiness was only significant in one of the cross-over trials (F 1,28.95 = 103.09; p < 0.01) ( Tempesta et al., 2014 ); whereas a marginal increase in daytime sleepiness was noted in the other cross-over trial, but the effect was not significant ( t = −1.890, p = 0.071, Cohen’s d = −0.39) ( Lin et al., 2020 ). On the other hand, the effect of partial sleep deprivation (4-hours for one night) on self-reported daytime sleepiness relative to healthy sleep opportunity was significant in 3 cross-over trials with a medium effect size ( Rossa et al., 2014 ; Schwarz et al., 2016 ; Schwarz et al., 2013 ). Also, the partial sleep deprivation as opposed to the healthy sleep opportunity condition displayed higher objective daytime sleepiness via the pupillary unrest test (5.7 ± 2.1 vs. 4.5 ± 2.1 mm/min, p = .002) with a medium effect size (Cohen’s d = 0.55) ( Schwarz et al., 2016 ).

3.4.4. Effect of sleep deprivation on affect

The effect of sleep deprivation on affect was only assessed in one trial using a between persons comparison ( Franzen et al., 2008 ). Those in the total sleep deprivation condition (n = 14) as opposed to the healthy sleep opportunity condition (n = 15) had a higher negative mood ( F = 4.76, p = .039), lower positive affect ( F = 4.78, p = .038), but the change in negative affect was not significant ( F = 1.74, p = .20) ( Franzen et al., 2008 ).

The effect of sleep deprivation on affect was assessed in 5 RCTs using a within-person comparison ( n = 178) ( Drake et al., 2001 ; Kaida & Niki, 2014 ; Lin et al., 2020 ; Rossa et al., 2014 ; Tempesta et al., 2014 ). The effect of one night of total sleep deprivation resulted in a significant negative effect on affect in 3 trials relative to the healthy sleep opportunity condition ( Drake et al., 2001 ; Kaida & Niki, 2014 ; Lin et al., 2020 ). Compared to a healthy sleep opportunity, both positive affect and negative affect were significantly reduced when participants were totally sleep deprived in one cross-over trial ( Lin et al., 2020 ) and partially sleep-deprived (4-hours one night) in another cross over trial ( Rossa et al., 2014 ). The effect size was small in the partial-sleep deprivation cross over trial ( Rossa et al., 2014 ), medium in one of the total sleep deprivation cross-over trials (Cohen’s d = 0.51) ( Lin et al., 2020 ), and not reported in the other two trials ( Drake et al., 2001 ; Kaida & Niki, 2014 ). Lastly, there was a significant interaction between sleep loss and negative affect in working memory performance, but not with PVT performance in Tempesta et al. (2014) ‘s cross-over trial of 25 young adults.

4. Discussion

In this systematic review, the effect of sleep deprivation on neurobehavioral functioning (psychomotor vigilance performance, affect, and daytime sleepiness) in young adults was examined. The primary aim of this study was to examine the effect of sleep deprivation on psychomotor vigilance performance. The largest effects with significant decrements on the most PVT metrics were found in total sleep deprivation studies ( Drake et al., 2001 ; Esposito et al., 2015 ; Franzen et al., 2008 ; Honn et al., 2020 ; Jewett et al., 1999 ; Kaida & Niki, 2014 ; Lin et al., 2020 ; Patanaik, Zagorodnov, Kwoh, et al., 2014 ; Robillard et al., 2011 ; Tempesta et al., 2014 ; Tucker et al., 2009 ; Van Dongen et al., 2004 ). There was a dose-response relationship between the rate of sleep loss and psychomotor vigilance performance measured via PVT. Also, adaptation occurred with a slower accumulation of sleep loss ( Drake et al., 2001 ; Jewett et al., 1999 ; Van Dongen et al., 2004 ). The short time constant that was observed in one of the trials (0h to 2h conditions) ( Jewett et al., 1999 ) indicates that the first few hours of sleep may serve to restore psychomotor vigilance decrements following sleep deprivation. This may partially explain why a nap affords recovery disproportionate to its duration ( Jewett et al., 1999 ).

The second aim of this systematic review was to determine how sleep deprivation affected daytime sleepiness. Daytime sleepiness was measured via self-report in a majority of the trials with the Karolinska Sleepiness Test or Stanford Sleepiness Test and objectively with the Multiple Sleep Latency Test and Pupillary Unrest Index ( Lüdtke et al., 1998 ) in two trials ( Franzen et al., 2008 ; Schwarz et al., 2016 ). Most of the trials included acute sleep deprivation, however in the trial where partial sleep deprivation was examined over 14-days ( Van Dongen et al., 2004 ), chronic partial sleep deprivation of 4 – 6 hours resulted in an initial elevation of self-report ratings on both the Stanford Sleepiness Scale and Karolinska Sleepiness Scale, but as the study progressed only minor further increases in self-report daytime sleepiness that did not mirror the decrements in PVT performance were observed. Even at the end of the 14 days, participants only reported feeling slightly sleepy ( Van Dongen et al., 2004 ). This suggests that there is an adaptation to chronic partial sleep deprivation especially considering the chronic partial sleep deprivation condition was compared to a total sleep deprivation condition ruling out the potential for a ceiling effect as the total sleep deprivation condition showed considerably greater levels of daytime sleepiness after two nights ( Van Dongen et al., 2004 ). Another consideration when assessing daytime sleepiness is that it might be intertwined with affect and related to the same latent construct making it difficult to differentiate perceptions of daytime sleepiness from mood; therefore, it is warranted to include physiologic measures more sensitive than self-report measures as suggested by Franzen et al, 2008 .

Regarding our final aim to determine the effect of sleep deprivation on affect, it must be highlighted that affect was only assessed in one-third of the studies. Also, the designs and instruments to measure affect varied, making it difficult to draw conclusions. Nonetheless, both partial and total sleep deprivation conditions resulted in worsened affect in the young adults in the selected studies, which is consistent with other young adult and adolescent studies ( Baum et al., 2014 ; Franzen et al., 2008 ; Haavisto et al., 2010 ). Studies where objective physiological and/or neural measures of affect were assessed provide additional verification of the emotional dysregulation following sleep deprivation. This was demonstrated in two of the trials in the current review with additional measures of pupillary affective response ( Franzen et al., 2008 ; Schwarz et al., 2016 ). In previous research, a 60% amplification in reactivity of the amygdala assessed using functional MRI (fMRI) was observed following one night of total sleep deprivation (n = 14) in response to negative pictures triggering emotions, when compared to a healthy sleep opportunity condition ( n = 12) ( Yoo et al., 2007 ).

Limitations

There are some limitations of this systematic review that should be considered. First, regarding sample characteristics, we included individuals free of medical, psychiatric, and sleep disorders with previous healthy weight and sleep schedules, limiting the generalizability of these findings. Second, although psychomotor vigilance performance was a common outcome across studies, only 6 used a parallel-group design, and with a lack of baseline and outcome data reporting, we could not conduct a meta-analysis. Baseline and some post-intervention values were not available to calculate mean change in these studies, so our results are fully based on a narrative review. Third, although outcomes were common via the PVT, the heterogeneity across designs, analyses, and objectives made the synthesis and analysis difficult. We recommend more transparent data reporting in the future, particularly through the inclusion of baseline data. This would allow for meta-analyses to be performed in the future, allowing the effects to be pooled to advance the science. Also, because of the different designs and analyses, a determination about reproducibility could not be made.

Objective assessments and physiologic measures (e.g., the Multiple Sleep Latency test and Pupillary Unrest Index) were more precise and sensitive, which may have affected the self-reported daytime sleepiness and affective outcomes. A larger effect size was reported for the physiologic measures (daytime sleepiness and affect regulation) as opposed to the self-report mood and PVT outcomes in one of the trials ( Franzen et al., 2008 ).

5. Conclusions

We determined that sleep deprivation degrades young adults’ neurobehavioral functioning. These results are congruent with adult and adolescent studies, where total sleep deprivation (as opposed to partial sleep deprivation) has a substantial detrimental effect on psychomotor vigilance performance, with the largest effects for vigilance tasks ( de Bruin et al., 2017 ; Lim & Dinges, 2010 ). The studies were all based on acute sleep deprivation, so it was not possible to determine if psychomotor vigilance deficits accumulate over time during chronic sleep deprivation, which is most consistent with real-world settings ( Goel et al., 2009 ). This is important as young adult brains are sensitive to sleep loss, as indicated by imaging studies examining the prefrontal cortex ( Chee & Choo, 2004 ). There is considerable evidence that the prefrontal cortex continues to develop into early adulthood which may affect speed of performance on psychomotor vigilance tasks, although this association has not been examined longitudinally ( Chee & Choo, 2004 ; Gied et al., 1999; Muzur et al., 2002 ). Thus, the effects of chronic sleep deprivation on the psychomotor vigilance performance of the developing brain remain unclear. Also, though our primary intention was to assess the effect of sleep deprivation on psychomotor vigilance performance via PVT, daytime sleepiness was only assessed in 10 and affect in 6 of the studies limiting the ability to comprehensively assess neurobehavioral function among young adults in the included studies.

The findings presented underscore the importance of measuring different neurobehavioral function metrics (e.g., psychomotor vigilance - cognitive performance via PVT, daytime sleepiness via self-report and objective measures, and affect) when studying their response to sleep and wakefulness. Larger RCTs that include an objective to examine the effect of sleep deprivation on neurobehavioral function under controlled conditions are needed to reveal predictors and negative effects of acute and chronic sleep deprivation in this high-risk group. Researchers should also consider including moderators (e.g., age, sex, dose) when these larger studies are available for meta-analysis. Nurses working across tertiary care and the community are well-positioned to take the lead on advocating for policies and practices promoting a healthy sleep opportunity and sleep education to optimize brain development in this age group.

• Total and partial sleep deprivation lead to significant decrements in neurobehavioral function (cognitive performance, affect, and sleepiness) in young adults.
• Adaptation to sleep loss can occur when it accumulates over time.
• The focus of the current literature is on short term sleep loss limiting the ability to draw inference to real world settings where sleep loss occurs at a more stable state over time (e.g., chronic partial sleep deprivation).
• The prefrontal cortex continues to develop until the late 20’s, thus the effects of sleep loss over time in the developing brain remain unclear.

Acknowledgements:

The authors would like to acknowledge the contributions of DG in screening for inclusion and assisting with quality assessment.

Funding Statement:

This work was supported by American Academy of Sleep Medicine Foundation (AASM), 220-BS-19 and the National Institute for Nursing Research (NINR), K99NR018886. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the AASM Foundation or NIH.

Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

CRediT authorship contribution statement: Stephanie Griggs: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Data Curation, Writing – original draft, Project administration, Funding acquisition. Alison Harper: Validation, Formal analysis, Investigation, Data Curation, Writing – original draft. Ronald L. Hickman: Supervision, Conceptualization, Methodology, Validation, Formal analysis, Investigation, Writing – review and editing, Project administration.

Declaration of competing interests: No conflict of interest has been declared by the authors.

Contributor Information

Stephanie Griggs, Case Western Reserve University, Frances Payne Bolton School of Nursing, Cleveland, Ohio, USA 44106.

Alison Harper, Case Western Reserve University, Frances Payne Bolton School of Nursing, Department of Anthropology, Cleveland, Ohio, USA 44106.

Ronald L. Hickman, Jr, Ruth M. Anderson Endowed Professor of Nursing and Associate Dean for Research Case Western Reserve University, Frances Payne Bolton School of Nursing, Cleveland, OH, USA 44106.

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Sleep is as essential to our daily needs as food and water. Although we may feel that sleep simply rests our tired bodies, our brain remains active throughout the night. Sleep plays a critical role in brain as well as physical functioning.

What Happens When We Sleep?

Our internal body clock, called a circadian clock, tells us when we are ready to sleep. There are actually several circadian clocks in the body, found in the brain and other organs. They are triggered by cues such as daylight (we feel alert) and darkness (we feel drowsy). These clocks can also be triggered by artificial bright light or stimulants like caffeine and alcohol that cause us to feel awake even if it is nighttime.

There are several phases of sleep our body experiences. They are classified as REM (rapid eye movement) and non-REM sleep. We cycle repeatedly through these phases about 4-6 times throughout the night, and it is not uncommon to wake up briefly between cycles.

Non-REM sleep

Stage 1. You transition from being awake to a restful state.

Stage 2. You are in a light sleep state. Your breathing, heart rate, and muscle movements slow down. Brain activity also slows, and your body temperature drops.

Stage 3. You are in a deep sleep state. This stage often occurs early in the sleep cycle immediately following light sleep. Your heart rate and breathing are the slowest during this phase, and you are not easily awakened. Events of the day are processed and stored in your memory. A lack of deep sleep can leave one feeling tired in the morning even if achieving an adequate duration of sleep.

During REM, your pupils twitch and move quickly from side to side underneath closed eyelids. Brain activity rises as you breathe faster and your heart rate increases. It is the phase of sleep when dreams are most common, and certain nerves signal your limbs to become temporarily paralyzed so you do not act out the dream. REM tends to occur later at night and into early morning. Memory is processed and stored during REM sleep.

Why do we dream?

Hormones that regulate sleep cycles.

There are various neurotransmitters and hormones released by the brain that send signals to promote sleep or wakefulness. [1] Many of these chemicals are stimulated by light or darkness.

• GABA is a neurotransmitter that decreases nerve cell activity, playing a major role in allowing the body to sleep.
• Adenosine is another neurotransmitter that gradually accumulates in the brain during the day, and at high concentrations makes us sleepy at night. Caffeine in coffee and other beverages can keep us awake as it blocks brain receptors for adenosine.
• Melatonin is a hormone released by the brain when it is dark. It travels to cells to tell the body to sleep. Sunlight or exposure to light inhibits the production of melatonin and increases the release of cortisol, which awakens us. If we are exposed to too much artificial light (such as the blue light emitted from smartphones or televisions) late at night, less melatonin may be released making it harder to fall asleep.
• Serotonin, the body’s “feel-good” chemical, is a neurotransmitter associated with both sleep and being awake. The brain releases this chemical during daylight but also uses it to form melatonin at night.
• Hormones that counteract sleep include norepinephrine, adrenaline, histamine, and cortisol. These are secreted in response to stress and cause the body to be awake and alert. If one experiences prolonged or chronic stress, the body releases adrenocorticotropic hormone (ACTH), which in turn releases cortisol. Levels of ACTH tend to be higher in people who have insomnia.  

Immediate Effects of Sleep Deprivation

About one-third of American adults do not get enough sleep each night, according to the Centers for Disease Control and Prevention. [2,3] Short sleep duration in adults is defined as less than 7 hours of sleep in 24 hours. About 40% of adults report unintentionally falling asleep during the day at least once a month, and up to 70 million Americans have chronic sleep problems. Because of the public health burden of poor sleep health, achieving sufficient sleep in children and adults was included as a goal in the Healthy People 2020 goals. [4]

Sleep helps to process your thoughts from the day as well as store memories, so a lack of good-quality sleep can lead to difficulty focusing and thinking clearly. You may feel tired, irritable, or anxious during the day. Performance at work or school may suffer. Your reaction time may be slowed, increasing the risk of driving accidents.

In children, insufficient sleep can lead to attention and behavior problems or hyperactivity. In the elderly, lack of sleep may decrease focus and attention, leading to a greater risk of falls, bone fractures, and car accidents.

There are several reasons people may get insufficient sleep:

• Poor sleep habits (watching television or using screens late at night, drinking caffeinated or alcoholic beverages at night, not following a regular sleep schedule).
• Your sleep environment is too noisy, too light or otherwise not conducive to sleep.
• You attempt to sleep outside of the body’s natural circadian clock (working an overnight shift and trying to make up for sleep during the day).
• You have a sleep disorder, such as sleep apnea, insomnia, or periodic limb movements that reduces deep or REM sleep or causes frequent awakenings.
• You have a medical condition such as heart, lung or kidney disease, or chronic pain, which causes frequent awakenings.

Sleep Deficiency and Disease Risk

If you experience continued sleep deprivation, you will develop a condition called sleep deficiency. This is a state in which you cannot make up the many lost hours of sleep. Sleep deficiency increases the risk of obesity, diabetes, cardiovascular disease, depression, and even early death.

Several studies show that sleep deprivation (i.e., regularly less than 7 hours of sleep a night) is a risk factor for obesity. A Nurses’ Health Study found an association between those who slept the least (5 hours or less a night) and having the highest BMI and greatest weight gain. [5] One reason may be a disruption in appetite hormones that regulate feelings of hunger (called ghrelin) versus satisfaction (called leptin). Ghrelin levels rise while leptin levels drop with lack of sleep; this can cause higher calories to be consumed due to experiencing strong hunger at the same time that one feels less satiated after eating. A preference for foods high in fat and carbohydrate has been observed. [6,7] The risk of hunger also increases simply by being awake longer, which prolongs the time from the last meal eaten to bedtime. [6] Insufficient sleep also can trigger the “reward” areas in your brain to crave high fat, high caloric foods. [8]

One may think that getting less sleep would mean more activity due to being awake longer and therefore using more calories. However, studies have found either no increase or very small increases in energy expenditure with sleep deprivation, and even a tendency towards reduced physical activity due to fatigue. [9] Less physical activity combined with the increased calorie intake associated with sleep deprivation increases the risk of obesity.

Other effects of poor sleep include increased fat storage in the belly area, higher body mass index, poorer quality diet, and decreased insulin sensitivity. [6,10] Interestingly, some studies have also shown that longer sleep times (more than 9 hours) are also associated with developing belly fat compared with sleeping 7-8 hours a night. [7]

Epidemiological and laboratory studies show a higher risk of diabetes mellitus with both too little sleep (less than 7 hours) and longer sleep durations (more than 9 hours). Metabolic changes may occur with chronic insufficient sleep, such as higher cortisol levels leading to increased blood glucose. Clinical studies have found both increased glucose and insulin levels (suggesting insulin resistance) and reduced insulin sensitivity in sleep-deprived individuals. [11] Disruption in the regulation of appetite hormones as seen with higher ghrelin and lower leptin levels may lead to increased food intake and weight gain, also increasing the risk of insulin resistance. [11]

Some people who have insufficient sleep have a condition called obstructive sleep apnea, which blocks breathing in the upper airway tubes, often because of increased fat in the tongue. Sleep apnea is independently associated with insulin resistance; a lack of oxygen while sleeping can cause oxidative stress and inflammation that are believed to progress toward insulin resistance. [11]

Both shorter and longer sleep durations are associated with cardiovascular diseases . [12,13] Proposed reasons include activation of the sympathetic nervous system and impaired endothelial function, which can lead to elevated blood pressure and hardening of arteries. There may also be greater release of pro-inflammatory cells and decreased immune function. Metabolic changes include a disruption in appetite hormones and circadian rhythms that lead to inflammatory conditions. [14]

• People sleeping less than 6 hours a night, particularly women, were 20-32% more likely to develop hypertension compared with those sleeping 7-8 hours a night. [12] Having 5 or less hours of sleep a night was associated with double the risk of developing hypertension in another study. [15]
• In a Nurses’ Health Study, the risk of heart disease was almost 1.4 times higher in women sleeping 5 hours or less a night and 9 hours or more a night compared with those sleeping 8 hours a night. [16]
• In postmenopausal women, those who slept 5 hours or less or 10 hours or more a night had a 25% and 45% increased risk of heart disease, respectively. [17]
• Individuals with inadequate sleep as well as long sleep durations showed an increased risk of strokes. [12]
• Individuals with poor sleep quality or insomnia symptoms are 40% more likely to develop hypertension [18]
• People with obstructive sleep apnea are at increased risk for stroke, heart attack, and heart failure.
• A Presidential Advisory from the American Heart Association included sleep health as part of its eight measures, “Life’s Essential 8,” to assess cardiovascular health. [19] It cites evidence showing that either too short or too long sleep durations are associated with heart disease. Their findings also show that chronically poor sleep is a risk factor for early death, is associated with poor psychological health, and can negatively affect blood pressure, inflammation, and regulation of blood glucose.

Poor sleep and insomnia (an inability to sleep or stay asleep) are associated with depression, especially if the insomnia becomes chronic. [20] Insomnia is also associated with increased likelihood of insomnia relapsing over time. Poor sleep quality can impair functioning, increase fatigue, and lead to mood changes. The reverse is also true in which depressive symptoms of intense sadness or hopelessness can interrupt sleep. Insomnia as well as oversleeping are common signs of clinical depression, according to the National Institute of Mental Health. [21] Treating the depression may lead to improvements in sleep quality. If there is an underlying medical disorder causing the insomnia such as obstructive sleep apnea or chronic pain, then treatment should address these first.

In 2021, authors of a cohort study sought to tease out the association of early brain changes and sleep changes by including younger patients 50 years of age. They followed 7,959 participants for up to 25 years and found that participants who were between the ages of 50-70 years and slept 6 hours or less a night showed a 30% higher risk of developing dementia in later life, compared with those who slept 7 hours. [40] The association was only slightly weaker when authors controlled for various factors independently associated with dementia like cardiometabolic status (high blood pressure, diabetes mellitus, body mass index, cardiovascular disease), sociodemographic variables (age, sex, ethnicity, education, marital status), health behaviors (smoking, alcohol, exercise, intake of fruits and vegetables), and mental health factors (depression). The authors did not find an association with longer sleep durations (8 or more hours) and dementia, though this may have been due to the low number of participants who slept longer durations.

Prospective cohort studies have found that both a chronic lack of sleep (less than 7 hours) and long sleep durations (more than 8 hours) are associated with greater risk of death from all causes. [7,13] Obstructive sleep apnea and insomnia are also associated with increased mortality. [22,23]   However, long sleep durations appear to be more associated with increased risk of mortality than inadequate sleep. [13] Some studies show that women may have greater risk of mortality related to short sleep durations than men. [24] Longer sleep times are associated with several factors that are associated with mortality, including fatigue, stress, obstructive sleep apnea, and increased inflammation of heart arteries. More research with randomized controlled trials is needed to better understand the reasons for these findings.

Medical Conditions that Interfere with Sleep

• Obstructive sleep apnea (OSA) —Symptoms of OSA include snoring or gasping for air that causes interruptions in sleep and prevention of good-quality sleep. Sleep apnea also causes oxygen levels to drop during sleep, which can pose a stress on the heart, brain and other organs. People with OSA may not be aware that they are awakening frequently in the night, but do not get refreshed sleep, feeling excessively sleepy or tired during the day. Continuous positive airway pressure (CPAP) devices may be prescribed, which provides pressurized air to the nose and throat, preventing the upper airway from collapsing. Another common treatment is dental devices that move the jaw forward and increasing the airway size. Obesity is a risk factor for OSA because carrying extra weight, particularly in the neck area, can contribute to obstructed breathing passages. About 70% of adults with OSA have obesity, and a significant improvement in OSA is seen with weight reduction. [7] OSA is a risk factor for insulin resistance, hypertension, type 2 diabetes, cardiovascular disease, and early mortality. [7]
• Restless leg syndrome —This condition is associated with discomfort in the legs accompanied by an urge to move, which disrupts sleep. It is believed that abnormal levels of the neurotransmitter dopamine may be responsible, so medications are given to correct this. In some cases, low levels of iron can result in this disorder.
• Insomnia —This condition is defined as the inability to sleep or stay asleep. An individual may have a hard time falling asleep, or may sleep but then awaken in the early morning and be unable to return to sleep. Short-term insomnia can be caused by stress or traumatic events (divorce, job loss, death of a loved one). Chronic or long-term insomnia may be caused by ongoing anxiety, working different work shifts that disrupt the body’s circadian rhythms, poor sleep habits, medical conditions that can interrupt sleep (chronic pain, gastroesophageal reflux disease), or medications that have a stimulating effect. Insomnia often can be treated with behavioral therapies, although sometimes sleep medications are prescribed.
• Genetic —Studies have found specific gene variants that are associated with insomnia. [25,26] The same genes for insomnia were also associated with higher levels of body fat, depression, and heart disease. Research has also found that sleep apnea clusters within families, and genes have been identified that appear to increase risk for sleep apnea as well as cardiovascular disease. [27] More research is needed in this area.

What if I work the night shift?

• Request to work the same shift several nights in a row, to avoid flipping between day and night shift schedules on consecutive days. This helps to regulate the circadian system.
• Commit to a consistent sleep schedule, darkening the bedroom with blackout shades, and creating a quiet atmosphere as much as possible. You might reduce light exposure even earlier by wearing sunglasses as soon as you leave work. To reduce noise, wear earplugs and use a white noise machine to block sounds.
• After finishing a night shift, try to return home and go to bed as soon as possible. Running errands, watching television, talking with family, or exercising can re-energize your body so that falling asleep becomes more difficult.
• Although it is tempting to run errands and attend medical appointments during the day when places are less crowded, try to minimize doing them immediately after work so that you can return home and honor your sleep schedule.
• Try to keep a set meal schedule. Do meal planning to ensure that quick easy meals are ready when you arrive home, and bring prepped meals/snacks to work for overnight shifts to prevent reliance on fast food and takeout meals. Try to avoid eating a large meal right before bed, which can increase the risk of reflux and indigestion.

Sleep Deficiency and Eating Behaviors

Epidemiological studies show that insufficient sleep is independently associated with a higher risk of obesity. Clinical studies of of sleep-restricted adults show an increased hunger and calorie intake when participants are allowed free access to food. [7] A preference for late evening or nighttime food intake and increased snacking has been observed. [9] There also appears to be a food preference for higher carbohydrate and fat foods, which could partly explain the overall higher calorie intake.

Changes in hormone levels that signal either hunger or satiety have also been observed in clinical sleep restriction studies. Leptin is a hormone associated with satisfaction. When food enters the stomach, leptin is released from fat cells and travels to the brain where it signals the body to stop eating by creating a sensation of fullness. People with obesity may actually have very high levels of leptin; the more body fat one has, the more leptin is produced in fat cells. However, a condition called leptin resistance may occur in which the brain does not receive the usual signal from leptin to stop eating. In response, more and more leptin is released. Lower leptin levels as well as high leptin levels suggesting leptin resistance have been observed in sleep-deprived adults. [7]

Ghrelin, the “hunger hormone,” typically has the opposing action of leptin. It is released in the gut and sends hunger signals to the brain when someone is not eating enough. About three hours after eating a meal, ghrelin levels drop. Clinical studies have found that sleep restriction leads to elevated ghrelin levels. [9]

Despite this interesting theory of poor sleep leading to changes in appetite hormone levels, other studies have found no changes and therefore the association is still inconclusive. [9] Conflicting findings may be due to differences in the study participants (e.g., age, gender) and differences in how the researchers defined the duration and severity of sleep restriction.

How Much Sleep Do We Need?

Sleep needs change as we age, with the average person generally requiring less sleep at older ages. However, specific sleep amounts vary by individual. According to the National Sleep Foundation and American Academy of Sleep Medicine (AASM), newborns need the most sleep, at 14-17 hours a day, followed by infants at 12-16 hours a day including naps. Toddlers need about 10-14 hours a day. Preteens and teenagers need about 8-12 hours a night, and adults about 7-8 hours a day. [30] A consensus by the AASM and Sleep Research Society recommends that adults should sleep 7 or more hours a night to promote optimal health. [31]

Despite these general recommendations on sleep duration, individual differences in sleep requirements exist. In most epidemiologic studies, increased risk of adverse health outcomes such as obesity, diabetes , and cardiovascular disease , has been observed among those who reported sleeping 5 hours or less per day, and 9 hours or more per day. Thus, a range of sleep hours (more than 5 and less than 9) is considered appropriate for most healthy adults.

Other factors such as quality of sleep are important, because just meeting the total recommended sleep hours may not be enough if one wakes up frequently in the night. A common belief is that lost sleep from a late night out or studying can be recovered by “sleeping in” another day or taking naps. However, both of these methods disrupt the body’s circadian rhythms and may deprive the body of deeper sleep stages. In fact, increased variability in how much sleep we get from night to night is associated with an increased risk of developing metabolic and heart diseases. [32] It is important to respond, whenever possible, to the body’s natural signals of sleepiness.

What about supplements, medicines, and other therapies for sleep?

Two popular herbal supplements, melatonin and valerian, are used as sleep aids. Melatonin has been shown to quicken time to sleep and have modest benefits on sleep duration and quality, but can cause daytime drowsiness. It is well tolerated in adults with few reported adverse events in doses up to 10 mg. The American Academy of Sleep Medicine (AASM) recommends the judicious use of melatonin for certain sleep and circadian disorders such as shift work disorder or jet lag. [33]

Valerian contains small amounts of GABA, a sleep-promoting neurotransmitter, and some studies have shown that valerian can improve sleep. However, other studies have found no difference in sleep when taking valerian compared with placebo, and there appears to be minimal benefit in those who have diagnosed insomnia. The AASM does not recommend valerian for insomnia disorder. [33]

It is important to note that supplements are not reviewed by the U.S. Food and Drug Administration for safety or effectiveness. Therefore doses and preparations of these herbs can vary widely. A study of 31 melatonin products found that the melatonin levels in the pills ranged between 83%-478% of the dose reported on the label. [33] More than 70% of the products varied from the labeled dose by more than 10%. If supplements are used, look for a label verifying its quality from a third-party, such as from the U.S. Pharmacopeia.

Sleep medicines

Common medicines prescribed for sleep include sedatives such as benzodiazepines (e.g., Valium, Xanax, Klonopin, Ativan*). They help with falling asleep initially, but tend to reduce the amount of deeper sleep. They are not recommended for long-term use because they can worsen insomnia, increase depression, and impair memory, and are associated with increased risk of falls, cancer, and early death. [34] Long-term use of benzodiazepines can promote psychological dependence, and there is a risk of addiction and abuse. [35] Tolerance can also develop over time, requiring larger doses to maintain their effectiveness. Because of these side effects, benzodiazepines are not recommended to treat insomnia in older adults. [35] There are other classes of sleep medications including non-benzodiazepines (e.g., Lunesta, Ambien) and antidepressants (e.g., Zoloft) that also quicken the time to fall asleep but may interfere with deeper sleep stages. Anticholinergic medications (e.g., Benadryl) can increase the risk for cognitive impairment and decline. Generally, sleep medicines are most effective when used occasionally or for a short time of less than one month. The American Academy of Sleep Medicine (AASM) recommends that cognitive behavioral therapy be used as the initial treatment for insomnia. [ *The inclusion of brand names is included for reference and does not constitute an endorsement. The Nutrition Source does not endorse any specific brands. ]

Other therapies

Randomized clinical trials have shown that cognitive behavioral therapies (CBT) for sleep such as minimizing napping during the day, relaxation training, breathing exercises, and sleep hygiene are highly effective and recommended as first-line treatments for insomnia. [35,33] They have been found more effective than medications for the long-term management of insomnia. People may be asked to keep a sleep journal to record sleep habits and activities performed around bedtime, which can help determine the most appropriate CBT.

Sleep Hygiene Tips  

• Set a sleep schedule and stick to it. Try to go to bed at night and awaken in the morning around the same times, even on weekends. This helps to regulate the body’s sleep cycles and circadian rhythms.
• Try to exercise at some point in the day but avoid vigorous activity (running, fast dancing, high-intensity interval training or HIIT) one hour before bedtime. Regular exercise of adequate intensity can promote muscle relaxation and deeper sleep later on.
• Try to avoid large meals, heavy snacking, or alcohol 2-3 hours before bed.
• If you are sensitive to caffeine, try to avoid drinking caffeinated beverages 4-6 hours before bedtime.
• Stop using electronic devices an hour before bed, especially those emitting blue light such as smartphones, tablets, and televisions.
• Schedule before-bed activities to signal that you are winding down, such as changing into pajamas and brushing teeth.
• Create a quiet, dark, relaxing environment in your bedroom. Dim the lights and turn off your cell phone’s sound and vibration modes if possible.
• Ensure a comfortable temperature, as feeling too hot or cold can disrupt sleep.
• Create calming bedtime rituals such as practicing deep breathing exercises, doing light yoga stretches, or listening to soothing relaxing music. Many meditation podcasts, apps, and YouTube videos offer these tools for free.
• If you awaken and can’t return to sleep, don’t stay in bed. Get up and do quiet relaxing activities, such as reading, until you feel tired enough to fall back asleep.  

Does exercising at night disrupt sleep?

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• Gangwisch JE, Heymsfield SB, Boden-Albala B, Buijs RM, Kreier F, Pickering TG, Rundle AG, Zammit GK, Malaspina D. Short sleep duration as a risk factor for hypertension: analyses of the first National Health and Nutrition Examination Survey. Hypertension . 2006 May 1;47(5):833-9.
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• Li X, Sotres-Alvarez D, Gallo LC, Ramos AR, Aviles-Santa L, Perreira KM, Isasi CR, Zee PC, Savin KL, Schneiderman N, Wassertheil-Smoller S. Associations of Sleep Disordered Breathing and Insomnia with Incident Hypertension and Diabetes: The Hispanic Community Health Study/Study of Latinos. American journal of respiratory and critical care medicine . 2020 Aug 6(ja).
• Lloyd-Jones DM, Allen NB, Anderson CAM, Black T, Brewer LC, Foraker RE, Grandner MA, Lavretsky H, Perak AM, Sharma G, Rosamond W; American Heart Association. Life’s Essential 8: Updating and Enhancing the American Heart Association’s Construct of Cardiovascular Health: A Presidential Advisory From the American Heart Association. Circulation . 2022 Jun 29:101161CIR0000000000001078.
• Fernandez-Mendoza J, Shea S, Vgontzas AN, Calhoun SL, Liao D, Bixler EO. Insomnia and incident depression: role of objective sleep duration and natural history. Journal of sleep research . 2015 Aug;24(4):390-8.
• National Institute of Mental Health. Depression. February 2018. https://www.nimh.nih.gov/health/topics/depression/index.shtml.  Accessed 7/31/20.
• Punjabi NM, Caffo BS, Goodwin JL, Gottlieb DJ, Newman AB, O’Connor GT, Rapoport DM, Redline S, Resnick HE, Robbins JA, Shahar E. Sleep-disordered breathing and mortality: a prospective cohort study. PLoS med . 2009 Aug 18;6(8):e1000132.
• Parthasarathy S, Vasquez MM, Halonen M, Bootzin R, Quan SF, Martinez FD, Guerra S. Persistent insomnia is associated with mortality risk. The American journal of medicine . 2015 Mar 1;128(3):268-75.
• Liu TZ, Xu C, Rota M, Cai H, Zhang C, Shi MJ, Yuan RX, Weng H, Meng XY, Kwong JS, Sun X. Sleep duration and risk of all-cause mortality: a flexible, non-linear, meta-regression of 40 prospective cohort studies. Sleep medicine reviews . 2017 Apr 1;32:28-36.
• Dashti HS, Jones SE, Wood AR, Lane JM, Van Hees VT, Wang H, Rhodes JA, Song Y, Patel K, Anderson SG, Beaumont RN, Bechtold DA, Bowden J, Cade B, Garaulet M, Kyle SD, Little MA, Loudon, AS, Luik AI, Scheer FAJL, Kpiegelhalder Kai, Tyrrell J, Gottleib DJ, Tiemeier H, Ray DW, Purcell SM, Frayling T, Redline S, Lawlor DA, Rutter MK, Weeden MN, Saxena R. Genome-wide association study identifies genetic loci for self-reported habitual sleep duration supported by accelerometer-derived estimates. Nature communications . 2019 Mar 7;10(1):1-2. Disclosure: FAJL Scheer received speaker fees from Bayer Healthcare, Sentara Healthcare, Philips, Kellogg Company, and Vanda Pharmaceuticals. MK Rutter reports receiving research funding from Novo Nordisk, consultancy fees from Novo Nordisk and Roche Diabetes Care, and modest owning of shares in GlaxoSmithKline.
• Lane JM, Jones SE, Dashti HS, Wood AR, Aragam KG, van Hees VT, Strand LB, Winsvold BS, Wang H, Bowden J, Song Y. Biological and clinical insights from genetics of insomnia symptoms. Nature genetics . 2019 Mar;51(3):387-93.
• Cade BE, Chen H, Stilp AM, Gleason KJ, Sofer T, Ancoli-Israel S, Arens R, Bell GI, Below JE, Bjonnes AC, Chun S. Genetic associations with obstructive sleep apnea traits in Hispanic/Latino Americans. American journal of respiratory and critical care medicine . 2016 Oct 1;194(7):886-97.
• Vallières A, Azaiez A, Moreau V, LeBlanc M, Morin CM. Insomnia in shift work. Sleep Medicine . 2014 Dec 1;15(12):1440-8.
• Shriane AE, Ferguson SA, Jay SM, Vincent GE. Sleep hygiene in shift workers: A systematic literature review. Sleep Medicine Reviews . 2020 May 20:101336.
• Paruthi S, Brooks LJ, D’Ambrosio C, Hall WA, Kotagal S, Lloyd RM, Malow BA, Maski K, Nichols C, Quan SF, Rosen CL. Consensus statement of the American Academy of Sleep Medicine on the recommended amount of sleep for healthy children: methodology and discussion. Journal of clinical sleep medicine . 2016 Nov 15;12(11):1549-61.
• Consensus Conference Panel, Watson NF, Badr MS, Belenky G, Bliwise DL, Buxton OM, Buysse D, Dinges DF, Gangwisch J, Grandner MA, Kushida C. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. Journal of Clinical Sleep Medicine . 2015 Jun 15;11(6):591-2.
• Huang T, Redline S. Cross-sectional and prospective associations of actigraphy-assessed sleep regularity with metabolic abnormalities: the Multi-Ethnic Study of Atherosclerosis. Diabetes Care . 2019 Aug 1;42(8):1422-9.
• Zhou ES, Gardiner P, Bertisch SM. Integrative medicine for insomnia. Medical Clinics . 2017 Sep 1;101(5):865-79.
• Markota M, Rummans TA, Bostwick JM, Lapid MI. Benzodiazepine use in older adults: dangers, management, and alternative therapies. InMayo Clinic Proceedings 2016 Nov 1 (Vol. 91, No. 11, pp. 1632-1639). Elsevier.
• Brewster GS, Riegel B, Gehrman PR. Insomnia in the older adult. Sleep medicine clinics . 2018 Mar 1;13(1):13-9.
• Kredlow MA, Capozzoli MC, Hearon BA, Calkins AW, Otto MW. The effects of physical activity on sleep: a meta-analytic review. Journal of behavioral medicine . 2015 Jun 1;38(3):427-49. *Disclosure: MW Otto has served as a paid consultant for MicroTransponder Inc., Concert Pharmaceuticals, and ProPhase; provided expert consensus opinion for Otsuka Pharmaceuticals, received royalty support for use of the SIGH-A from ProPhase, and received book royalties from Oxford University Press, Routledge, and Springer.
• Kovacevic A, Mavros Y, Heisz JJ, Singh MA. The effect of resistance exercise on sleep: a systematic review of randomized controlled trials. Sleep medicine reviews . 2018 Jun 1;39:52-68.
• Stutz J, Eiholzer R, Spengler CM. Effects of evening exercise on sleep in healthy participants: A systematic review and meta-analysis. Sports Medicine . 2019 Feb 14;49(2):269-87.
• Thomas C, Jones H, Whitworth-Turner C, Louis J. High-intensity exercise in the evening does not disrupt sleep in endurance runners. European Journal of Applied Physiology . 2020 Feb 1;120(2):359-68.
• Sabia S, Fayosse A, Dumurgier J, van Hees VT, Paquet C, Sommerlad A, Kivimäki M, Dugravot A, Singh-Manoux A. Association of sleep duration in middle and old age with incidence of dementia. N ature Communications . 2021 Apr 20;12(1):1-0.

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Everybody loses a night of sleep sometimes — on campus, especially during exams. According to Nora D. Volkow , who gave a talk at Radcliffe’s Knafel Center Thursday titled “The Sleep-Deprived Human Brain,” a single sleepless night is probably harmless. But the cumulative effects of sleep deprivation may be more dangerous than is currently understood.

Volkow, now the director of the National Institute on Drug Abuse at the National Institutes of Health, was a pioneer in positron emission tomography (PET) brain imaging, and helped carry out early studies confirming the toxic effects of cocaine. At Harvard, she reported on two sets of brain-imaging studies that shed light on the way sleep deprivation interferes with cognition, as well as its possible links to dementia and Alzheimer’s disease.

Her work in drug research, she said, led to an investigation of sleep patterns. One toxic property of cocaine is that it interferes with sleep.

“If you give cocaine to an animal, it is the only drug that will cause it to forgo sleep, and the animals ultimately died because they did not survive this,” she said. Yet lack of sleep itself produces some of the same adverse effects that drugs do: It disrupts memory, inhibits alertness, and can contribute to obesity.

“It also results in accidents, and there are more fatalities associated with improper sleep behavior than there are with alcohol,” said Volkow, whose presentation was a 2017–2018 Kim and Judy Davis Dean’s Lecture in the Sciences..

Volkow’s work included a look at the effects of sleep deprivation on the dopamine system, which regulates alertness and overall brain function. After running magnetic resonance imaging and PET scans on sleep-deprived human subjects, she found that lack of sleep inhibited certain parts of dopamine transmission: Brain cells were able to release dopamine, but not to receive it.

“The decrease in dopamine receptors can be likened to going to an auditorium when nobody is there,” she said.

Changes linked to sleep deprivation didn’t necessarily create tiredness, but could potentially lead to more dangerous conditions.

“When people are sleep-deprived they are less likely to regulate their desires, and they engage in impulsive behaviors,” Volkow said.

Continued sleeplessness allows levels of beta amyloid to grow to dangerous levels, said Volkow, but one night of good sleep could reverse the process.

One drug that appears to actually be advantageous — at least in the short term — is caffeine. Drinking coffee, she said, may temporarily increase dopamine receptors, thus countering the effects of sleeplessness.

A second, as-yet-unpublished set of studies that Volkow quoted suggests a link between sleep deprivation and dementia. It is known that the brain’s glymphatic system flushes out toxins during sleep. Studies in mice have shown that fluids from blood vessels, the spine, and other parts of the body flow to the brain during sleep, helping to remove a toxic protein called beta amyloid from brain tissue. (These proteins tended to accumulate when the animal was sleep-deprived.) Unlike mice, humans can survive more than a few days without sleep, but beta amyloid buildup has been linked to dementia and Alzheimer’s disease.

Volkow decided that similar studies could be done in humans. This research showed that even one night without sleep increased the accumulation of beta amyloids — though Volkow was surprised to find that the increases were found only in the right hippocampus. One night of good sleep could reverse the process, she said, but continued sleeplessness could push the toxins to dangerous levels.

“We can document an association between poor sleep quality and a higher beta-amyloid burden in the brain,” she said. “This is consistent with prior reports, and we show that these are independent from the higher burden associated with genetic risks.” This, she suggested, shows a scientific reason why sleep is necessary for a healthy brain.

Volkow said clinical research has too often neglected the importance of sleep, for which the evidence is clear, she added, of an important role “in the capacity of the brain to renew itself.”

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Why You Should Make a Good Night’s Sleep a Priority

Poor sleep habits and sleep deprivation are serious problems for most high school and college students. This guide offers important tips on how—and why—to improve your sleep hygiene.

The time you spend in high school and college can be both fun and rewarding. At the same time, these can be some of the busiest years of your life.

Balancing all the demands on your time—a full course load, extracurricular activities, and socializing with friends—can be challenging. And if you also work or have family commitments, it can feel like there just aren’t enough hours in the day. 

With so many competing priorities, sacrificing sleep may feel like the only way to get everything done. 

Despite the sleepiness you might feel the next day, one late night probably won’t have a major impact on your well-being. But regularly short-changing yourself on quality sleep can have serious implications for school, work, and your physical and mental health.

Alternatively, prioritizing a regular sleep schedule can make these years healthier, less stressful, and more successful long-term.

The sleep you need versus the sleep you get

According to the National Sleep Foundation , high school students (ages 14-17) need about eight to 10 hours of sleep each night. For young adults (ages 18 to 25), the range is need between seven and nine hours.

How do you know how much sleep you need within this range? 

According to Dr. Edward Pace-Schott, Harvard Summer School and Harvard Medical School faculty member and sleep expert, you can answer that question simply by observing how much you sleep when you don’t need to get up.

“When you’ve been on vacation for two weeks, how are you sleeping during that second week? How long are you sleeping? If you’re sleeping eight or nine hours when you don’t have any reason to get up, then chances are you need that amount or close to that amount of sleep,” says Pace-Schott. 

Most students, however, get far less sleep than the recommended amount. 

Seventy to 96 percent of college students get less than eight hours of sleep each week night. And over half of college students sleep less than seven hours per night. The numbers are similar for high school students; 73 percent of high school students get between seven and seven and a half hours of sleep .

Of course, many students attempt to catch up on lost sleep by sleeping late on the weekends. Unfortunately, this pattern is neither healthy nor a true long-term solution to sleep deprivation. 

And what about those students who say that they function perfectly well on just a couple hours of sleep?

“There are very few individuals who are so-called short sleepers, people who really don’t need more than six hours of sleep. But, there are a lot more people who claim to be short sleepers than there are real short sleepers,” says Pace-Schott.

Consequences of sleep deprivation

The consequences of sleep deprivation are fairly well established but may still be surprising.

For example, did you know that sleep deprivation can create the same level of cognitive impairment as drinking alcohol? 

According to the CDC , staying awake for 18 hours can have the same effect as a blood alcohol content (BAC) of 0.05 percent. Staying awake for 24 hours can equate to a BAC of 0.10 percent (higher than the legal limit of 0.08 percent). 

And according to research by AAA , drowsy driving causes an average of 328,000 motor vehicle accidents each year in the US. Drivers who sleep less than five hours per night are more than five times as likely to have a crash as drivers who sleep for seven hours or more.  

Other signs of chronic sleep deprivation include:

• Daytime sleepiness and fatigue
• Irritability and short temper
• Mood changes
• Trouble coping with stress
• Difficulty focusing, concentrating, and remembering

Over the long term, chronic sleep deprivation can have a serious impact on your physical and mental health. Insufficient sleep has been linked, for example, to weight gain and obesity, cardiovascular disease, and type 2 diabetes.

The impact on your mental health can be just as serious. Harvard Medical School has conducted numerous studies, including research by Pace-Schott, demonstrating a link between sleep deprivation and mental health disorders such as anxiety and depression.

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Importance of sleep for high school and college students

As difficult as it is to prioritize sleep, the advantages of going to bed early and getting quality sleep every night are very real.

College students who prioritize sleep are likely to see an improvement in their academic performance.

If you are well rested, you will experience less daytime sleepiness and fatigue. You may need less caffeine to stay awake during those long lectures. And you will also find you are more productive, more attentive to detail, and able to concentrate better while studying.

But the connection between sleep and academic performance goes well beyond concentration and attentiveness.

“Sleep is very important for consolidating memories. In any sort of experimental setting, study results show better performance if you learn material and then sleep on it, instead of remaining awake. So there’s lots and lots of evidence now indicating that sleep promotes memory strengthening and memory consolidation,” says Pace-Schott. 

There is also a strong connection between sleep quality and stress.

Students who prioritize sleep are better able to cope with the stress that comes with being an active student. 

“It’s a vicious circle where the more stressed you get, the less you sleep, and the less you sleep, the more stressed you get. And in the long term, that can lead to serious psychiatric problems,” says Pace-Schott.

In the worst case scenario, the combination of lack of sleep and stress can lead to mental health disorders such as depression, general anxiety disorder, and potentially even post-traumatic stress disorder.

But prioritizing sleep can create a positive feedback loop as well. 

Establishing a sleep schedule and adequate sleep duration can improve your ability to cope with stress. Being active and productive will help you get more done throughout the day, which also reduces feelings of stress.

And the less stressed you feel during the day, the better you will sleep at night. 

Tips for getting more sleep as a student

The key to getting a good night’s sleep is establishing healthy sleep habits, also known as sleep hygiene.

The first step is deciding to make sleep a priority. 

Staying ahead of coursework and avoiding distractions and procrastination while you study is key to avoiding the need for late night study sessions. And prioritizing sleep may mean leaving a party early or choosing your social engagements carefully. 

Yet the reward—feeling awake and alert the next morning—will reinforce that positive choice. 

The next step is establishing healthy bedtime and daytime patterns to promote good quality sleep.

Pace-Schott offers the following tips on steps you can take to create healthy sleep hygiene:

• Limit caffeine in close proximity to bed time. College students should also avoid alcohol intake, which disrupts quality sleep.
• Avoid electronic screens (phone, laptop, tablet, desktop) within an hour of bedtime. 
• Engage in daily physical exercise, but avoid intense exercise within two hours of bedtime.
• Establish a sleep schedule. Be as consistent as possible in your bedtime and rise time, and get exposure to morning sunlight.
• Establish a “wind-down” routine prior to bedtime.
• Limit use of bed for daily activities other than sleep (e.g., TV, work, eating)

Of course, college students living in dorms or other communal settings may find their sleep disturbed by circumstances beyond their control: a poor-quality mattress, inability to control the temperature of your bedroom, or noisy roommates, for example. 

But taking these active steps to promote healthy sleep will, barring these other uncontrollable circumstances, help you fall asleep faster, stay asleep, and get a more restorative sleep.

And for students who are still not convinced of the importance of sleep, Pace-Schott says that personal observation is the best way to see the impact of healthy sleep habits. 

“Keep a sleep diary for a week. Pay attention to your sleep in a structured way. And be sure to record how you felt during the day. This can really help you make the link between how you slept the night before and how you feel during the day. It’s amazing how much you will learn about your sleep and its impact on your life.” 

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No-sleep challenge: The dangers of sleep deprivation

by Adam Taylor, The Conversation

Most of us will be all too familiar with that dopey, groggy feeling of being tired after a restless night. Some social media users have taken tiredness to the extreme, however, by taking part in what they call a "no-sleep challenge."

One 19-year-old Youtuber, Norme, live streamed his attempt to break a world record for consecutive days without sleep. At the 250-hour mark, viewers voiced concerns about Norme's health and well-being, but he eventually finished with a "no sleep" time of 264 hours and 24 minutes.

Norme's attempt earned him bans from social media platforms YouTube and Kick . But, despite his claims to have beaten the world record, his ordeal was not enough to beat the last Guinness World Record holder Robert Mcdonald, who racked up 453 hours —almost 19 days!—in 1986.

In 1997, Guinness World Records stopped monitoring the record for the longest time without sleep for safety reasons—and they were quite right. Going without sleep for extended periods of time can prove extremely dangerous.

Adults should aim for more than seven hours' sleep per night on a regular basis. Chronic inability to get sufficient sleep is associated with increased risk of multiple conditions such as depression, diabetes, obesity, heart attack , hypertension and stroke.

Sleep is an important part of our daily routine. It enables many of our bodily systems to rest and focus on repair and recovery .

During the first three stages of sleep, the parasympathetic nervous system —which regulates rest and digestion—takes control. This reduces reduces heart rate and blood pressure .

In the final stage, the rapid eye movement (REM) stage, heart activity increases and eyes move —this stage is key to cognitive functions such as creativity, learning and memory. Alcohol or caffeine consumption prior to bed can disturb these sleep cycles.

Sleep deprivation can be acute or chronic. Acute deprivation can happen over a day or two.

While it may seem like a short period of time, 24 hours of sleep deprivation can cause a greater degree of functional impairment than being just over the drink-drive limit. Symptoms of acute sleep deprivation can include puffy eyes or dark under-eyes , irritability, cognitive decline, brain fog and food cravings .

During the second day without sleep, symptoms increase in intensity and behavioral changes occur, as well as a further decline in cognitive functions. The body's need for sleep becomes stronger causing "microsleeps"— involuntary naps lasting around 30 seconds.

The body's need for food increases as well as physiological responses such as systemic inflammation and impaired immune response , making us more susceptible to illness.

The third 24-hour period can trigger a desperate urge to sleep, increasing likelihood of longer microsleeps, depersonalisation —feelings of detachment from reality—and hallucinations . Once into day four of sleeplessness, all symptoms become much worse progressing to sleep deprivation psychosis where you're unable to interpret reality and possess a painful desire to sleep.

Recovery from sleep deprivation varies from person to person, with a solid overnight sleep being enough for some to recover. For others it can take days or weeks.

However, studies have shown that recovery sleep often doesn't reverse the metabolic changes that can cause weight gain and a decrease in insulin sensitivity , even from relatively short periods of sleep deprivation.

Shift workers can be continually sleep deprived. Night shift workers typically average one-to-four hours' less sleep per day than people whose work time falls within daylight hours—and this can increase their risk of early death .

In fact many studies have shown too little sleep is associated with an increased risk of death . But too much sleep has also been associated with an increased risk of death .

It's best for health, then, to avoid the social media challenges and instead opt for good sleep hygiene to get your seven-to-nine hours of quality shut-eye. Your body will thank you for it.

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Best Pillows for Side Sleepers: A Complete Guide in 2024

Our Reviews Team researched hundreds of pillow models and mystery shopped more than 30 pillow brands in person and online. Here’s how we made our selections:

• Analyzed costs, benefits, features, and brand policies, such as returns and trial periods
• Consulted sleep specialists, including doctors, occupational therapists, and physical therapists, for insight on choosing the best pillows for side sleepers
• Identified and tested key factors for an objective measure of features, like motion transfer, pressure relief, edge support, and cooling technologies
• We’ve personally rested on and tested each pillow against these factors for an unbiased assessment. Our selections were also medically reviewed to ensure each brand and model is appropriate for our readers’ needs.
• We regularly update our content with new pillows based on our constant testing, as well as updates to pricing, sales, new models, and more.

Learn more about how we test the best pillows for side sleepers .

Key Takeaways

• Our top pick for the “Best Pillow for Side Sleepers Overall” is the Brooklinen Marlow Pillow due to its adjustable loft (height) and firmness, which provide good neck support and spinal alignment.
• Maintaining spinal alignment during sleep is crucial to avoiding neck and back pain.
• The price range for the pillows in this review is $49–$159, depending on materials and features.
• Nearly 50% of people are side sleepers, making it crucial to find a pillow that offers the right support and comfort for this common position.
• Effective temperature regulation is important for many sleepers to get a good night’s sleep.

A regular good night’s sleep is crucial, as quality sleep helps support overall health , cognitive function, and emotional well-being. Research indicates something as simple as using a supportive pillow tailored to a sleeper’s needs can help improve sleep quality . 

Most people find comfort in sleeping on their sides. Our survey of 600 respondents found side sleeping was the most preferred position, with 48% of respondents categorizing themselves as side sleepers (compared to only 14% identifying as stomach sleepers, 17% as back sleepers, and 21% as combination sleepers). 

For side sleepers, the right pillow is vital to maintaining spinal alignment and preventing discomfort. Chris Peloquin , a physical therapist at Luna Physical Therapy in Denver, told us, “It’s important for side sleepers to reduce lateral [side] force on the spine, a common source of back pain in this position. A well-chosen pillow can support the head, neck, and shoulders, ensuring the spine remains neutral, which helps reduce the risk of waking up with pain or stiffness.”

In this article, we will review four top-rated pillows specifically designed for side sleepers. We will delve into the features, benefits, and our tester insights for each pillow to help you make an informed choice for a better night’s sleep.

Best pillow for side sleepers in 2024

• Brooklinen Marlow Pillow : Best Pillow for Side Sleepers Overall
• The Otter : Best Cooling Pillow for Side Sleepers
• Luxome LAYR : Best Pillow for Side Sleepers with Neck Pain
• TEMPUR-Neck Pillow : Best Pillow for Side and Back Sleepers

Brooklinen Marlow Pillow: Best Pillow for Side Sleepers Overall

• Price : $49 for standard-size and $69 for king-size before discounts
• Material: Memory foam and polyester fiber
• Brand’s firmness rating: Adjustable
• Trial period: 365 nights
• Shipping: Free ground shipping on orders more than $75; starts at $6 for orders less than $75
• Warranty: Two years
• Offers financing: Yes

Customer service

You can reach Brooklinen customer service by:

• Phone: Call 646-798-7447, available seven days a week from 10 a.m. to 9 p.m. ET
• Email: [email protected] , available seven days a week from 9 a.m.to 9 p.m. ET
• Chat: 24/7 live chat on the website

Payment options 

Brooklinen accepts Visa, Mastercard, American Express, Discover, Shop Pay, PayPal, Diners Club, JCB, Elo, and UnionPay. Financing is available through Shop Pay and Afterpay.

Our expert take on the Brooklinen Marlow Pillow 

The Brooklinen Marlow pillow stands out as a versatile option for side sleepers due to its unique design and materials. This pillow features a blend of shredded foam and polyester fiber fill, offering a unique combination of support and plushness. It’s this blend that caused our testers to say this was one of the most comfortable pillows they tried—the polyester fiber helps plug the gaps between the shredded foam, making the Marlow pillow feel more uniform and less lumpy than other pillows.

The Marlow also has an adjustable loft (height). Zippers on the side help sleepers customize the pillow’s height and firmness to three different levels. Simply unzip both sides for maximum loft and softness, only one side for medium loft and softness, and keep both sides zipped for lowest loft and maximum firmness. The more you zip, the more compressed (and more firm) the pillow becomes. And unlike other adjustable pillows, no material is removed from the Marlow, making it a less messy option.

For side sleepers, the Marlow pillow performs well across different body types: 

• Lighter-weight (less than 130 pounds) sleepers should appreciate the softest feel and highest loft when both ends are unzipped, which ensures excellent neck alignment and a cushiony feel. 
• Average-weight (130–250 pounds) sleepers benefit from the same neck support, whether using the pillow with one side unzipped for a medium-firm feel or both sides unzipped for a softer experience. 
• Higher-weight (250 pounds or more) sleepers should find all three loft settings work well, maintaining neck alignment and providing sufficient cushion.

Our testers were pleased with the Marlow Pillow’s performance in testing. They gave the pillow a perfect comfort rating of five out of five due to the pillow’s customizable design and soft, supportive materials. It also scored well in support, earning four out of five due to its adjustable loft options and material blend. Durability was also impressive, with a four out of five rating due to its high-quality shredded memory foam fill and a quilted cover. If you do find the pillow isn’t durable enough, Brooklinen offers a generous 365-night sleep trial and a two-year warranty.

Despite its adjustability, the Brooklinen Marlow pillow may be too firm or high for stomach sleepers. Stomach sleepers typically need a softer and shorter pillow to keep their spine aligned. 

Our tester on the Brooklinen Marlow pillow:

“I found the Marlow pillow very comfortable for sleeping on my side, particularly with the sides zipped up. I felt supported and my neck felt in alignment with my spine.”

Our sleep expert’s take

Who may love it

• Side sleepers seeking adjustable loft and firmness 
• Those who need solid neck support
• Sleepers who appreciate high-quality, hypoallergenic materials

Who may want to avoid it

• Full-time stomach sleepers
• Those looking for machine-washable pillows

The Otter: Best Cooling Pillow for Side Sleepers

• Price : $120 for queen-size and $140 for king-size before discounts
• Material: Memory foam and polyester
• Brand’s firmness rating: Adjustable
• Trial period: 100 nights
• Shipping: Free shipping
• Warranty: Five years

You can reach Lagoon customer service by:

• Email: [email protected]
• Chat: Automated chat via the bottom right corner of the website, available 24/7.
• Submit a contact form on the website

Lagoon accepts Visa, Mastercard, American Express, Discover, Shop Pay, Google Pay, JCB, Elo, and UnionPay. Financing is available through Shop Pay.

Our expert take on the Lagoon The Otter pillow 

Studies show pillows with cooling properties may improve sleep quality . Designed with a gel-infused CertiPUR-US-certified memory foam and polyester fiber fill, this pillow offers both support and temperature regulation. The shredded material has good airflow throughout from the infused gel, and the pillow’s bamboo cover helps naturally regulate temperature. Our tester noted the pillow increased in temperature only by about five degrees during tests, which indicates “exceptional” temperature regulation.

The Otter is adjusted by adding or removing fill material. For side sleepers, this pillow provides both support and comfort across different body types: 

• Lighter-weight sleepers should appreciate how the memory foam contours the head and neck, providing neck alignment and a plush feel. 
• Average-weight sleepers will likely benefit from the pillow’s buoyant support, which keeps tension off the neck. 
• Higher-weight sleepers should also find ample neck support, which can be adjusted by fluffing the pillow or adding or removing fill as needed.

The Otter pillow performs well in several other key areas. Testers rated support as four out of five, since the pillow’s adjustable fill makes it versatile for side, back, but maybe not for combination sleepers—because they switch positions throughout the night, combination sleepers may find this pillow not responsive enough for their different positions. 

Comfort received a four out of five, as the pillow offers a balance of firmness and plushness, with the option to adjust the fill to achieve the desired loft. Off-gassing ⓘ The chemical odor given off from a new mattress—the smell is harmless and is usually gone within the first few days is rated four out of five, with only a slight initial odor that dissipates quickly. The pillow is made with hypoallergenic materials, earning it a four out of five rating for allergens. Cleaning and care are rated five out of five, as both the cover and inner pillow are machine-washable. Lastly, the Otter pillow offers a 100-night sleep trial and a five-year warranty. 

Our tester on the Otter pillow:

“I love how the memory foam fill contours around the head and neck to help with support. Great neck alignment and plush feel.” 

• Side sleepers seeking a cooling, adjustable pillow
• People with allergies who need to wash their pillow covers often
• Customers who appreciate sustainable, eco-friendly materials
• People who are sensitive to initial off-gassing odors
• Combination sleepers who may need to make constant fill adjustments

Luxome LAYR: Best Pillow for Side Sleepers with Neck Pain

• Price : $120 for standard-size and $150 for king-size before discounts
• Material: Down alternative and memory foam
• Trial period: 30 nights
• Warranty: None

You can reach Luxome customer service by:

• Email: [email protected] , available Monday through Friday from 9 a.m. to 5 p.m. ET

Luxome accepts Visa, Mastercard, American Express, Discover, Shop Pay, PayPal, Amazon Pay, and Google Pay, as well as Diners Club, Elo, JCB, and UnionPay. Financing is available through Klarna and Shop Pay.

Our expert take on the Luxome LAYR pillow 

The best pillows for neck pain tend to offer a good mix of adjustability and strong support. The Luxome LAYR pillow has both and is a top choice for side sleepers with neck pain due to its design and range of customization options. This pillow comes with three different adjustable inserts to fine-tune height and firmness. Not only can you make adjustments by switching out the different inserts, but the inserts themselves can be adjusted by removing some of the material (two of the inserts are solid pieces of memory foam and one is shredded memory foam).

Upon unboxing, our tester noted the Luxome LAYR comes with eight total pieces: the main zipper pillowcase, two memory foam layers, one down alternative layer, one down alternative and shredded memory foam layer, and three zipper bags for storing unused layers.

For side sleepers, the Luxome LAYR pillow provides tailored support that can help reduce neck pain for most body types: 

• Lighter-weight sleepers should find the customizable layers allow for precise adjustments to achieve the right loft and firmness. 
• Average-weight sleepers may benefit from the pillow’s ability to keep their neck aligned while offering a cushioned feel that supports the head and neck. 
• Higher-weight sleepers might also appreciate the adjustable inserts, which help ensure the pillow can accommodate different body types and provide consistent support throughout the night.

The Luxome LAYR pillow’s performance in various categories is impressive. It scored high in support, due to its adjustable design that caters to the specific needs of side sleepers. The pillow’s combination of memory foam and latex help contour the head and neck while providing a responsive and supportive feel. Durability is also a strong point, with high-quality materials ensuring the pillow maintains its shape and support over time. The pillow is hypoallergenic and designed to minimize allergens, making it a suitable option for those with sensitivities. Also, the pillow’s cover is removable and machine-washable (unlike the Brooklinen Marlow).

Like some other pillows in this review, the Luxome LAYR may not be suitable for stomach sleepers. Although it’s adjustable, stomach sleepers typically need a soft, short pillow—firmer and higher pillows tend to push their spine up and cause a slight arc in their back that may cause pain in the morning. The Luxome LAYR is also one of the most expensive pillows in this list, so if budget is your top concern we recommend the Brooklinen Marlow (about half the cost of every other pillow in this review). 

Our tester on the Luxome LAYR pillow:

“The Luxome LAYR pillow’s adjustable layers allowed me to find the perfect height and firmness. It significantly reduced my neck pain.”

• Side sleepers with neck pain
• Those who want fully customizable height and firmness
• People with allergies who prefer hypoallergenic materials and machine-washable pillow covers
• Stomach sleepers
• Those who prefer a single-material pillow
• People looking for a budget-friendly option

TEMPUR-Neck Pillow: Best Pillow for Side and Back Sleepers

• Price : $119 for small, $129 for medium, $159 for large before discounts
• Material: Solid foam
• Brand’s firmness rating: Extra firm
• Trial period: None

You can reach TEMPUR-Pedic customer service by:

• Phone: Call 800-821-6621, available Monday through Friday from 8 a.m. to 8 p.m. ET, Saturday from 9 a.m. to 6 p.m. ET, and Sunday from 10 a.m.to 6 p.m. ET
• Chat: Live chat on the website, available 24/7
• Visit a store: Find a location near you on their website

TEMPUR-Pedic accepts Visa, Mastercard, American Express, and Discover. Financing is available through Wells Fargo on orders of $1,000 or more.

Our expert take on the TEMPUR-Neck Pillow 

The TEMPUR-Neck Pillow offers a body-hugging solution for both side and back sleepers. Its solid, molded memory foam construction follows the natural curvature of the body, providing firm support to keep the neck aligned with the spine. Available in three sizes (small, medium, and large), this pillow caters to various body types.

For side sleepers, the TEMPUR-Neck Pillow is particularly effective in maintaining proper neck alignment, despite its firmer feel. Lighter-weight side sleepers might prefer the small size to avoid excessive lift, while average- and higher-weight sleepers may benefit from the medium or large sizes. 

Back sleepers should also find this pillow supportive and comfortable, as it cradles the neck without elevating it too much. The mix of support and comfort also makes this pillow a good candidate for one of the best pillows for back pain . 

The pillow scored well in several performance categories. It offers good support with a perfect rating of five out of five, helping to promote spinal alignment for both side and back sleepers. Durability is rated four out of five, reflecting the high-quality dense foam that maintains its shape over time. Comfort received a four out of five, as the pillow’s firmness is well-suited for side and back sleepers, but might take some getting used to. 

The TEMPUR-Neck Pillow scored lower in temperature regulation (two out of five) due to memory foam’s tendency to trap heat, but the company does offer a cooling cover for an extra $20. The standard cover is hypoallergenic, removable, and washable, leading to a cleanliness and care rating of five out of five. Although it comes with a five-year limited warranty, it does not come with a sleep trial.

Stomach sleepers will probably not like this pillow. Its body-hugging design cradles the neck and shoulders for side sleepers, but stomach sleepers will likely experience a rounded back (the opposite of an arched back), which may strain the spine.

Our tester on the TEMPUR-Neck pillow:

“Even though this pillow is technically for side and back sleepers, I prefer it for back sleeping. While the firmer feel is good on my side, it feels wonderful while lifting the neck and head when lying on my back”

• Side and back sleepers needing firm neck support
• Those who prefer a pillow that conforms to their body’s natural curves
• Sleepers seeking pressure relief in the neck and shoulders
• Hot sleepers
• Those who prefer a soft, plush pillow may not like the extra-firm feel

How we test the best pillows for side sleepers

Our Reviews Team recommends products and services we believe provide value to the lives of our readers. As we perform our in-depth research, we interview industry experts to provide the most accurate review possible. 

We evaluate each pillow’s suitability for back pain by testing for firmness, support, and pressure relief. Pillows that keep the spine in alignment with lower back support will score the highest.

Firmness is crucial in determining how well a pillow can support the neck and head, which directly affects spinal alignment. Adjustable pillows can help sleepers of all types align their spines, so we included several adjustable models in this article.

We evaluate the firmness by:

• Using standardized firmness scales to measure how much the pillow compresses under weight
• Testing how well the pillow maintains its shape and firmness over time
• Gathering feedback from our testers with different sleep positions and body types to ensure a broad assessment of firmness levels

Side sleepers usually benefit the most from medium or medium-firm mattresses. See our picks of the best mattresses for side sleepers for more information.

Support is a key factor in a good night’s sleep. A supportive pillow ensures the head, neck, and spine remain in proper alignment throughout the night. Foam is a particularly supportive material, so you will see many pillows with foam construction in this review. We assess support by:

• Measuring the pillow’s ability to maintain spinal alignment across different sleeping positions
• Ensuring the pillow provides the loft needed to support each sleeping position
• Testing the pillow’s responsiveness to movement and its ability to adapt to different shapes and weights

Pressure Relief

Pressure relief is essential for reducing strain on the shoulders and hips—two common areas of pressure for side sleepers. We test pressure relief by:

• Using pressure mapping ⓘ A mat with sensors that detects pressure buildup when someone lies across it to identify areas of high pressure and how well the pillow cushions these points
• Evaluating the materials used in the pillow, such as memory foam or latex, which are known for their pressure-relieving properties
• Conducting long-term use tests to see how the pillow performs over extended periods

To learn more about our testing, review our sleep methodology .  

We continuously test new pillows each month to ensure we provide you with the most up-to-date information possible. By staying current with the latest products and innovations, we aim to offer the best options tailored to your needs.

How to choose a pillow for side sleepers 

Selecting the right pillow as a side sleeper involves considering several important factors to ensure the best support and comfort. Here are the top aspects to keep in mind:

Firmness 

Firmness is crucial for side sleepers. A pillow that is too soft won’t provide enough support, leading to misalignment of the neck and spine. On the other hand, a pillow that is too firm can cause pressure to build up. The ideal firmness for most side sleepers is medium to firm, which offers the right balance of support and comfort, helping maintain proper spinal alignment throughout the night.

Loft/Height 

The loft of the pillow is another critical factor. Side sleepers need a higher loft to fill the space between the mattress and their head and neck to keep their spines aligned. A pillow with adjustable loft options is a good choice, allowing you to customize the height to your preference and body type.

Materials 

The materials used in a pillow have a big impact on its comfort, support, and durability. Memory foam and latex are popular choices for side sleepers because they contour the head and neck, providing consistent support. Pillows made with cooling materials, such as gel-infused foam or breathable fabrics, can also help regulate temperature, creating a more comfortable sleep environment.

Trial period and warranty 

A pillow’s durability is essential, especially for maintaining its supportive qualities over time. High-quality materials tend to last longer and provide consistent support. When selecting a pillow it’s important to have the opportunity to test the pillow in your own home to ensure it meets your needs. Many reputable pillow manufacturers offer a trial period, allowing you to experience how the pillow performs over time, as it may take several nights to adjust and determine if it provides the right support and comfort. A generous trial period (we recommend a 100-night minimum) ensures you can return or exchange the pillow if it doesn’t meet your expectations.

A good warranty (we recommend a one-year minimum) indicates a manufacturer’s confidence in their product. Warranties for pillows can vary, but a standard period is usually between one to five years. Some higher-quality pillows may come with even longer warranties. 

When evaluating a warranty, consider what it covers—common aspects include defects in materials and workmanship. A comprehensive warranty protects your investment, ensuring you receive a product that lasts and performs as promised.

Cost/budget

Cost is an important consideration when choosing a pillow, as prices can vary significantly depending on materials, brand, and extra features. While high-quality pillows often come with a higher price tag, they may provide better support, comfort, and durability, making them a worthwhile investment. Budget-friendly options are available, but they may not offer the same level of support or durability. 

When evaluating your budget, consider the long-term benefits of a well-made pillow, including improved sleep quality and reduced pain or discomfort. It’s often better to invest a bit more in a pillow that meets your specific needs and will last longer.

Best type of pillow material for side sleepers 

Choosing the right pillow material is essential for side sleepers to ensure support and comfort. Different materials offer unique benefits, from contouring support to breathability. Understanding the characteristics of each type can help you find the right pillow for your needs.

Memory foam pillow

Memory foam pillows are popular among side sleepers due to memory foam’s ability to contour the head and neck, providing personalized support. This material helps maintain spinal alignment and reduces pressure, which can ease pain and discomfort. Memory foam pillows also tend to retain their shape well over time.

Latex pillow

Latex pillows are another good option for side sleepers, since latex is known for its responsiveness and natural support. Latex pillows provide a good balance of firmness and comfort, promoting proper spinal alignment. Also, latex is naturally hypoallergenic and resistant to dust mites, making it a great choice for those with allergies or sensitivities.

Down pillow

Down pillows offer a softer, more luxurious feel, which can be appealing to some side sleepers. While down pillows provide good comfort, they may not offer as much support or loft as memory foam or latex pillows. 

Down alternative/polyfiber pillow

Down alternative or polyfiber pillows mimic the softness of down while being hypoallergenic and more affordable. These pillows provide a plush feel and may be a good option for side sleepers who prefer a softer pillow without compromising on comfort. While they may not offer the same level of contouring support as memory foam or latex, they can still provide enough loft and cushioning for a good night’s sleep.

Compare the best pillows for side sleepers, as of 2024

Bottom line 

The Brooklinen Marlow Pillow stands out as the best overall choice for its balance of comfort and support. The Otter offers excellent cooling properties, making it good for those who sleep hot. For those experiencing neck pain, the Luxome LAYR provides targeted support to soothe discomfort. Lastly, the TEMPUR-Neck Pillow is ideal for those who alternate between side and back sleeping, offering versatile support. 

Ultimately, weighing factors like cost, firmness levels, materials, and trial periods are critical when shopping for the best pillow for side sleepers. All the pillows on this list have been tested by our Reviews Team, so you can make an informed decision about which one is right for you.

Additional sleep resources

• Best mattress for sciatica
• Best mattress for arthritis
• Best mattress for hip pain
• Best mattress for shoulder pain
• Best mattress for fibromyalgia
• Best pillows for neck pain

Frequently asked questions

Side sleepers should look for a medium-to-firm pillow. This level of firmness provides the necessary support to keep the head, neck, and spine aligned, preventing discomfort and pain. A pillow that is too soft may not offer enough support, causing the head to sink too low and misaligning the spine.

Side sleepers should use a pillow that offers sufficient support and maintains spinal alignment. Memory foam and latex pillows are excellent choices because they contour the head and neck, providing personalized support. Down alternative/polyfiber pillows can also be suitable for those who prefer a softer feel but still need good loft and cushioning.

A side sleeper pillow should be thick enough to fill the gap between the neck and the mattress, typically around 4 to 6 inches. The ideal thickness depends on body type and shoulder width, but the goal is to keep the head and neck aligned with the spine, ensuring comfort and preventing strain.

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• How Sleep Affects Your Health. National Heart, Lung, and Blood Institute. June 15, 2022. Found on the internet at https://www.nhlbi.nih.gov/health/sleep-deprivation/health-effects
• Is your pillow hurting your health? Harvard Health Publishing. Feb. 15, 2021. Found on the internet at https://www.health.harvard.edu/pain/is-your-pillow-hurting-your-health
• Carmon, Kiara, et al. 1125 Use of a Pillow Designed to Help Users Feel Cool Improves Objective Sleep Quality and Perceived Sleep. Sleep. April 20, 2024. Found on the internet at https://academic.oup.com/sleep/article/47/Supplement_1/A483/7655132
• NCOA Adviser. Mattress Survey. 600 Respondents. Conducted Using Pollfish. Launched Jan. 3, 2024