Is Short Sleep Bad for the Brain? Brain Structure and Cognitive Function in Short Sleepers.

Recent years have seen a dramatic increase in the number of papers that have examined the relationship between selfreported sleep duration and health-related effects. The annual number of papers bearing the words sleep duration as part of the title increased from approximately three per year in the 1990s to more than 50 in 2008. These investigated the relationship between self-reported sleep duration and a large number of health-related conditions such as diabetes, cardiovascular morbidity, hypertension, metabolic syndrome and obesity, cancer, psychiatric disorders, neurological disorders and mortality (see a recent meta-analysis on the relationship between mortality and self-reported sleep duration and an accompanying editorial in Gallicchio and Kalesan, 2009; Grandner and Patel, 2009). Generally, both short sleep ( 8 h) were associated with detrimental health-related effects. Of note, most of these studies were not designed to investigate sleep-related effects. In many, selfreported sleep duration relied upon a single question and no information was provided on daytime sleep versus night-time sleep, nor on possible differences between weekdays and weekend sleep duration. These limitations raised the question of what is the true meaning of self-reported short or long sleep. Do they reflect actual physiological sleep amounts, or are they perhaps subjective indicators of functional states? The present issue of JSR includes two papers that investigated the relationship between self-reported sleep duration and cognitive functioning in large populations in Finland and Spain. One of them (Kronholm et al., 2009) provides interesting information on the meaning of subjective long and short sleep duration. They investigated the relationship between selfreported sleep factors such as sleep duration, insomnia, use of sleeping medications, probable sleep apnoea and fatigue and tiredness, with cognitive functioning in 5177 people older than 30 years from a cross-sectional representative sample of the adult population in Finland. Cognitive functioning was assessed objectively by verbal fluency, and encoding and retaining verbal material. In this study, short and long sleep duration and fatigue and tiredness were independent statistical predictors of low objectively measured cognitive functioning, even after controlling for health and socioeconomic factors. Sleep factors accounted for only a small proportion of the variation in the objective cognitive tests but for a much larger proportion of the variation in subjective cognitive function. Short sleep was associated with insomnia and depression, as well as with cardiovascular morbidities, while long sleep was associated with the use of neuroleptics, cerebrovascular and circulatory diseases and diabetes. Notably, a separate analysis of a subgroup of 2201 participants who did not report any illness and who also reported good, or relatively good, subjective health revealed that after adjustment for sociode

Much of what we assume about the effects of short sleep duration on neural reward processing derives from total sleep deprivation studies. Although total sleep deprivation appears rare, habitual short sleep is common: 30% of working US adults report habitually sleeping ≤ 6 hours/night. It remains largely unknown whether habitual short sleepers exhibit similar reward processing brain activation patterns to those observed following total sleep deprivation in prior studies. Therefore, our aim was to test objectively reward processing brain activation patterns associated with self-reported habitual short sleep duration in a large sample. Nine hundred and fifty-two adult participants from the Human Connectome Project database were grouped on reported habitual short (≤6 hours) vs. medium-length (7-9 hours) sleep duration using the Pittsburgh Sleep Quality Index (PSQI). Reward processing brain activation was examined using a gambling task during functional magnetic resonance imaging (fMRI). Subject-level covariates for age, sex, continuous sleep duration, daytime dysfunction, and PSQI total score are provided as supplemental analyses. Brain activation patterns revealed expected reward processing-related activation for age and sex. However, activation for sleep duration, dysfunction, and PSQI score did not correspond to those evident in previous total sleep deprivation studies. Self-reported short sleep duration, perceived sleep-related dysfunction, and sleep quality via PSQI do not appear to be meaningfully associated with activation in well-described regions of the human neurobiological reward circuit. As these findings are counter to prior results using experimental sleep deprivation, future work focused on more direct comparisons between self-reported sleep variables and experimental sleep deprivation appears warranted.

Sleep duration and daytime sleepiness in a large sample of Brazilian high school adolescents

The human body has adapted to daily changes in dark and light such that it anticipates periods of sleep and activity. Deviations from this circadian rhythm come with functional consequences. Thus, 17 hours of sustained wakefulness in adults leads to a decrease in performance equivalent to a blood alcohol-level of 0.05%;[1] the legal level for drink driving in many countries.[2] Rats deprived of sleep die after 32 days,[3] and, with longer periods of sleep deprivation, this would also be the case in human beings. Indeed, sleep deprivation is a common form of torture.[4] Given the readily observable effects of sleep in everyday life, it is not surprising that there has been scholarly interest in sleep since the beginning of recorded history.[5] Sleep epidemiology as a subject in its own right has a recognisable history of just over 30 years,[6] with the first modern epidemiological studies of sleep disturbances appearing around 1980.[7;8] Nevertheless, a PubMed search for terms “sleep/insomnia” and “epidemiology” shows that the cumulative number of papers on the subject over the past 10 years is already about 10,000. Although this is less than for standard risk factors, such as obesity (>60,000) and smoking (50,000)(Figure 1), the annual number of papers on sleep epidemiology is rising rapidly (Figure 2). This issue of IJE includes a review[9] of the first comprehensive textbook of Sleep Epidemiology,[10] and the purpose of our Editorial is further to highlight recent developments to give the reader an idea why the coming years are likely to see an increasing interest in sleep studies. Figure 1 Exposures AND Epidemiology 2000–2010 Figure 2 Sleep/insomnia AND Epidemiology by year Why the upsurge in interest? There are several reasons for an increase in interest in sleep from an epidemiological perspective. First, sleep problems are associated with accidents and human errors. It has been estimated that 10–15% of fatal motor-vehicle crashes are due to sleepiness or driver fatigue. Furthermore, by 2020 the number of people killed in motor-vehicle crashes is expected to double to 2.3 million deaths worldwide, of which approximately 230,000–345,000 will be due to sleepiness or fatigue.[11] It has been estimated that nearly 100,000 deaths occur each year in US hospitals due to medical errors and sleep deprivation have been shown to make a significant contribution.[12] Similarly, in a national sample in Sweden of over 50,000 people interviewed over 20 years disturbed sleep almost doubled the risk of a fatal accident at work.[13] Second, sleep problems are common. Population studies show that sleep deprivation and disorders affect many more people worldwide than had been previously thought. A recent study found 20% of 25–45 year-olds slept “90 minutes less than they needed to be in good shape”.[14] Insomnia is the most common specific sleep disorder, with ‘some insomnia problems over the past year’ reported by approximately 30% of adults and chronic insomnia by approximately 10%.[15] Prevalence of obstructive sleep apnoea, characterized by respiratory difficulties during sleep, is also very high with estimates of 9–21% in women and 24–31% in men.[16;17] Third, sleep problems are likely to increase. The rapid advent of the 24/7 society involving round-the-clock activities and increasing night time use of TV, internet and mobile phones mean that adequate sleep durations may become increasingly compromised. Some data suggest a decline in sleep duration of up to 18 minutes per night over the past 30 years.[18;19] Complaints of sleeping problems have increased substantially over the same period, with short sleep (<6 hours/night) in full-time workers becoming more prevalent.[19;20] As more shift work is required to service 24/7 societies the proportion of workers exposed to circadian rhythm disorders, such as shift work sleep disorder, and their effects on health and performance is likely to rise. Sleep architecture is known to change with age; slow-wave (or deep) sleep decreases and lighter sleep increases. Other changes include increases in nocturnal sleep disruption and daytime sleepiness. As the proportion of elderly people in populations across the world increases, these changing sleep patterns will raise the prevalence of sleep disorders. Similarly, the increasing worldwide obesity epidemic and the prevalence of obstructive sleep apnoea, which is over double among the obese, ensure sleep disorders will be of increasing public health importance in lower as well as high income countries.[16;21] Fourth, sleep problems are associated with short and long-term effects on health and well-being. Immediate effects at the individual level relate to well-being, performance, daytime sleepiness and fatigue. Longer term, evidence has accumulated of associations between sleep deprivation and sleep disorders and numerous health outcomes including premature mortality, cardiovascular disease, hypertension, inflammation, obesity, diabetes and impaired glucose tolerance, and psychiatric disorders, such as anxiety and depression. As this evidence represents the core of Sleep Epidemiology, we provide below a snapshot on key findings.

Sleep patterns and sleep problems in children are not only influenced by a large number of biological and psychologic factors but also by cultural and social factors. Little is known about similarities and differences in sleep patterns and sleep problems among children across countries. We attempted to compare sleep patterns and sleep problems among schoolchildren from 2 countries with distinctive cultural contexts: the United States and China. The data come from 2 cross-sectional surveys in 3 elementary schools of Jinan City, People's Republic of China, and 3 elementary schools from a suburban school district in southeastern New England, United States. The Chinese sample consisted of 517 elementary school children (grades 1 to 5), and the US sample consisted of 494 elementary school children (grades kindergarten through 4). We used the Children's Sleep Habits Questionnaire (CSHQ) to assess children's sleep patterns and sleep problems as reported by parents. Parents of the Chinese sample completed a Chinese version of the CSHQ. For children in both the US and Chinese samples, reported bedtime was delayed and sleep duration decreased with increasing age. Compared with the US children (grades 1-4), Chinese children went to bed approximately half an hour later (9:02 vs 8:27 pm) and woke up half an hour earlier (6:28 vs 6:55 am), resulting in an average sleep duration that was 1 hour less (9.25 vs 10.15 hours). Chinese children were rated significantly higher than the US children on almost all CSHQ scales, indicating more sleep problems in Chinese children. Common sleep problems observed for all children were difficulty falling asleep, having a fear of sleeping in the dark, sleep talking, restless sleep, teeth grinding during sleep, and daytime sleepiness. Shorter daily sleep duration was associated with difficulty falling asleep, struggling at bedtime, and trouble sleeping away for the US children, and with going to bed at different times and having a fear of sleeping alone for Chinese children. Short sleep duration was a main predictor of daytime sleepiness for Chinese children, whereas restless sleep and snoring predicted daytime sleepiness for the US children. As reported by parents, children in China went to bed later and woke up earlier and their sleep duration was 1 hour shorter than the US children. Chinese children were reported to have more sleep problems than their US counterparts. Daytime sleepiness was determined by sleep duration only for those who slept insufficiently. Unique school schedules and sleep practices may contribute to the differences in the sleep patterns and sleep problems of children from the United States and China.

BackgroundWhereas short and problematic sleep are associated with psychological problems in adolescence, causality remains to be elucidated. This study therefore utilized the discordant monozygotic cotwin design and cross‐lagged models to investigate how short and problematic sleep affect psychological functioning.MethodsAdolescent twins (N = 12,803, 13–20 years, 42% male) completed questionnaires on sleep and psychological functioning repeatedly over a two‐year interval. Monozygotic twin pairs were classified as concordant or discordant for sleep duration and trouble sleeping. Resulting subgroups were compared regarding internalizing problems, externalizing problems, and subjective well‐being.ResultsCross‐sectional analyses indicated associations of worse psychological functioning with both short sleep and problematic sleep, and cross‐lagged models indicate bidirectional associations. Longitudinal analyses showed that an increase in sleep problems experienced selectively by one individual of an identical twin pair was accompanied by an increase of 52% in internalizing problem scores and 25% in externalizing problem scores. These changes were significantly different from the within‐subject changes in cotwins with unchanged sleep quality (respectively, 3% increase and 5% decrease). Psychological functioning did, however, not worsen with decreasing sleep duration.ConclusionsThe findings suggest that sleep quality, rather than sleep duration, should be the primary target for prevention and intervention, with possible effect on psychological functioning in adolescents.

Short and long sleep durations are common behaviors that could predict several cardiovascular diseases. However, the association between sleep duration and atrial fibrillation (AF) risk is not well-established. AF is preventable, and risk prevention approaches could reduce its occurrence. Investigating whether sleep duration could predict AF incidence for possible preventive interventions and determining the impact of various lifestyle and clinical characteristics on this association to personalize such interventions are essential. Herein, we investigated the association between sleep duration and AF risk using a prospective cohort study and a meta-analysis of epidemiological evidence. Data of 6898 people, aged 30-84years, from the Suita Study, were analyzed. AF was diagnosed during the follow-up by ECG, medical records, checkups, and death certificates, while a baseline questionnaire was used to assess sleep duration. The Cox regression was used to compute the hazard ratios (HRs) and 95% confidence intervals (CIs) of AF risk for daily sleep ≤ 6 (short sleep), ≥ 8 (long sleep), and irregular sleep, including night-shift work compared with 7h (moderate sleep). Then, we combined our results with those from other eligible prospective cohort studies in two meta-analyses for the short and long sleep. In the Suita Study, within a median follow-up period of 14.5years, short and irregular sleep, but not long sleep, were associated with the increased risk of AF in the age- and sex-adjusted models: HRs (95% CIs) = 1.36 (1.03, 1.80) and 1.62 (1.16, 2.26) and the multivariable-adjusted models: HRs (95% CIs) = 1.34 (1.01, 1.77) and 1.63 (1.16, 2.30), respectively. The significant associations between short and irregular sleep and AF risk remained consistent across different ages, sex, smoking, and drinking groups. However, they were attenuated among overweight and hypertensive participants. In the meta-analyses, short and long sleep durations were associated with AF risk: pooled HRs (95% CIs) = 1.21 (1.02, 1.42) and 1.18 (1.03, 1.35). No signs of significant heterogeneity across studies or publication bias were detected. Short, long, and irregular sleep could be associated with increased AF risk. In the context of predictive, preventive, and personalized medicine, sleep duration should be considered in future AF risk scores to stratify the general population for potential personalized lifestyle modification interventions. Sleep management services should be considered for AF risk prevention, and these services should be individualized according to clinical characteristics and lifestyle factors. The online version contains supplementary material available at 10.1007/s13167-022-00275-4.

Objectives/Goals: This review examined if sleep duration is associated with established Alzheimer’s disease (AD) fluid biomarkers, such as amyloid-β peptides (Aβ40 and Aβ42), total-tau (t-tau), phosphorylated tau (p-tau181 and p-tau217), neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP). Methods/Study Population: We searched PubMed, CINAHL, and SCOPUS through September 15, 2024, using keywords and appropriate subject headings related to AD, fluid biomarkers, and sleep. The search was developed and conducted in collaboration with a medical librarian. We also searched Google Scholar and screened the reference lists of relevant reviews. Two independent reviewers screened 1,657 peer-reviewed articles, of which 21 met the inclusion criteria (14 with biomarkers measured in cerebrospinal fluid [CSF] and 7 in blood). Two review authors independently extracted study details from included articles using a standardized data extraction template. Results/Anticipated Results: Sample sizes ranged from 18 to 4,712 participants. Sleep duration was assessed using self-reported measures in 8 studies and objective measures in 13. For the 14 studies using CSF biomarkers, lower Aβ42 (3/14), Aβ40 (1/14), or the ratio (1/14) were associated with either short or long sleep duration; t-tau (3/14) and p-tau181 (4/14) levels were mostly associated with short sleep. For the 7 blood-based biomarker studies, Aβ42 (2/7), Aβ40 (2/7), and the ratio (3/7) had mixed results with either short or long sleep. T-tau (1/7) and p-tau181 (1/7) levels were associated with long sleep; NfL (2/7) was associated with both short and long sleep. Six studies reported nonlinear relationships, with both short and long sleep associated with unfavorable biomarker profiles. None of the studies investigated p-tau 217 or GFAP. Discussion/Significance of Impact: Our results suggest that the relationship between sleep duration and AD fluid biomarkers is very complex, and it highlights the importance of sleep in AD risk assessment and prevention. The inconsistency in findings stresses the need for standardized study design and measurement methods to clarify causality and inform clinical guidelines.

Sleep — An Affair of the Heart

Introduction: Discrimination may contribute to sleep disparities, and subsequent adverse cardiovascular health. Despite the higher prevalence of insomnia among women, particularly historically minoritized women compared to men, limited studies examine the association between discrimination and insomnia and sleep duration. Methods: Among 26,616 women (Race/Ethnicity: Asian = 323; Black = 457; Hispanic= 258; White=25,287) in the Women’s Health Study stress follow-up cohort (Mean age =72.3 + 6.1 years), we investigated the relationship of discrimination with insomnia and sleep duration and tested education and income as effect modifiers. Insomnia was self-reported as trouble falling asleep OR waking after sleep onset 3+/week and daytime sleepiness 3+/week. Sleep duration was defined according to weekday and weekend bed and wake times, and categorized as short (&lt;7 hours), recommended ( &gt; 7 and &lt;9 hours), and long ( &gt; 9 hours). Everyday discrimination (e.g., treated with less courtesy or respect, received poorer service, etc.) frequency was divided into tertiles then dichotomized as high (upper tertile) and low (lower &amp; middle tertile). Results: Insomnia, and short and long sleep duration were reported by 11%, 11%, and 15% of women, respectively, and high levels of discrimination were reported by 40% of women. There was a higher proportion of Asian and Black women who reported high discrimination compared to Hispanic and White women (53.2% and 57.3% vs 39.8% and 38.4%, respectively). Women reporting high vs. low discrimination were more likely to have insomnia and short sleep duration, but less likely to have long sleep [Insomnia Adjusted Prevalence Ratio (aPR): 1.33, 95% CI: 1.28-1.38; Short Sleep (aPR): 1.14, 95% CI:1.09-1.19; Long Sleep (aPR): 0.96, 95% CI: 0.95-0.97)]. Associations of discrimination with insomnia and short sleep duration were pronounced among Hispanic and White, but not Asian and Black women, and those of higher education ( &gt; bachelors vs &lt;bachelors) and income ( &gt; $50,000 vs &lt;$50,000). Conclusions: Discrimination may be a target for reducing the prevalence of insomnia and short sleep duration among women. Individuals of higher socioeconomic status may have increased vulnerability to the effects of discrimination on sleep.

Short and long sleep duration and risk of drowsy driving and the role of subjective sleep insufficiency

BackgroundAppropriate sleep duration is essential for maintaining normal cognitive function, but evidence is scarce in rural elderly population. This study aims to determine the associations between sleep duration and cognitive function among older adults in rural China.MethodsThis population-based cross-sectional study used data from the Confucius Hometown Aging Project in Shandong, China. Data on demographics, lifestyles, and chronic health conditions were collected through questionnaire surveys, clinical examinations, and laboratory tests. Sleep duration per day was classified into four groups (≤5 h, 6 h, 7 h, and ≥8 h). The Mini-Mental State Examination (MMSE) was used to assess the global and domain-specific cognitive function. Linear and logistic regressions were performed to determine the associations between sleep duration and cognitive function.ResultsCompared with 6 h sleep per day, sleep ≤5 h per day was associated with a higher odd of cognitive impairment with odds ratio (95% confident interval) being 1.70 (1.05, 2.74), but the association was attenuated and insignificant after the adjustment of covariates. Compared to those with 6 h sleep, individuals reporting short (≤5 h) or long (≥ 8 h) sleep duration per day had a lower MMSE score, and the adjusted β coefficient (95% confidence interval) was −0.36 (−0.71, −0.02) for sleep ≤5 h and −0.68 (−1.06, −0.30) for sleep ≥8 h. The patterns were similar for cognitive subdomains in orientation, attention and calculation.ConclusionsOur study showed that abnormal sleep duration was associated with poor cognitive function in older adults in China. Specifically, longer or shorter sleep duration was associated with lower cognitive function.

Introduction Excessive daytime sleepiness (EDS) affects 10-20% of the population and is associated with cardiovascular diseases (CVD) and mortality. However, EDS is heterogeneous, associated with both short and long sleep duration. It is unclear whether each subtype is related to CVD. Methods To understand the association of EDS subtypes (stratified by sleep duration) with incident myocardial infarction (MI), we perform multivariable Cox proportional hazards regression on MI using longitudinal medical record data of 471,991 individuals free of CVD at baseline from the UK Biobank. Baseline EDS and sleep duration were assessed by self-reported questionnaires. Results After adjusting for multiple social-demographic and behavioral factors, EDS with long sleep (³9 hours) was associated with a 91% increased incidence of MI (HR=1.91, 95% CI 1.34-2.71) compared to healthy sleep pattern (sleeping 6-9 hours without sleepiness), while EDS with normal (6-9 hours) or short sleep (≤6 hours) was not associated with incident MI. Long sleep without sleepiness was associated with a 39% increase in incident MI (HR=1.39, 95% CI 1.14-1.71). The association of EDS with long sleep was not explained by chronotype, insomnia, sleep apnea, depression, hypertension, or type 2 diabetes, but was confounded with self-reported overall health conditions (HR=1.46, 95% CI 1.02-2.08 after adjustment). Conclusion Our study suggests the previous association evidence of EDS increasing risk of MI may be primarily driven by its long sleep subtype (high “sleep propensity”), but the underlying mechanisms are unclear. Future work is needed to understand whether there are targetable interventions for this novel sleep phenotype that may improve cardiovascular health. Support (If Any) This research has been conducted using the UK Biobank Resource under Application Number 6818. Funding supports: NHLBI R35HL135818 and R01HL153814.

Whether short or insufficient sleep are risk factors for new-onset nocturnal gastroesophageal reflux (nGER). In this 10-year longitudinal study, adult general-population women in Uppsala, Sweden, answered questionnaires on sleep, nGER, and other conditions on 2 occasions. Participants at baseline totaled 6,790, while participants at follow-up totaled 4,925. "Short sleep" was defined as sleeping < 6 hours/night and "insufficient sleep" was defined as reporting an average actual sleep duration below 80% of the self-estimated need for sleep duration but without "short sleep." nGER was defined as reporting heartburn or acid reflux after going to bed sometimes, often, or very often. The confounding factors-age, body mass index, physical activity, caffeine intake, smoking habits, alcohol dependence, depression, anxiety, and snoring-were defined from the questionnaire. At baseline, 839 participants reported short sleep and 1,079 participants were defined as having insufficient sleep. Both participants with insufficient sleep and short sleep had nGER more often than those with sufficient sleep (26% vs 17% vs 10%, respectively). At follow-up, a new onset of nGER was twice as common among those with insufficient or short sleep at baseline and follow-up, compared with those with sufficient sleep at baseline and follow-up, even after adjusting for confounding factors (odds ratio 2.0 [1.5-2.8], P < .001). Insufficient sleep and short sleep are associated with nGER. Persistent insufficient and/or short sleep independently increases the risk of developing nGER over a 10-year follow-up. Women seeking treatment for nGER should be questioned about their sleep habits to identify insufficient sleep as a possible causative factor. Emilsson OI, Al Yasiry H, Theorell-Haglöw J, Ljunggren M, Lindberg E. Insufficient sleep and new onset of nocturnal gastroesophageal reflux among women: a longitudinal cohort study. J Clin Sleep Med. 2022;18(7):1731-1737.

Introduction Adverse childhood experiences (ACEs) are potentially traumatic events that occur before age 18, including abuse, neglect or witnessing violence in the home or community. ACE exposure has been associated with poor sleep and chronic diseases in adulthood. Leveraging data from the Southern Community Cohort Study (SCCS), a large cohort of predominantly low-income adults, we investigated ACE exposure in childhood with sleep duration in adulthood. Methods The SCCS enrolled predominantly Black adults age 40-79 from 12 southeastern US states between 2002-2009. SCCS participants self-reported sleep duration at baseline. The follow-up survey conducted from 2012-2015 included a 10-item ACEs scale. Sleep duration was categorized as short (&amp;lt; 7 hours), healthy (7-9 hours), or long (&amp;gt;9 hours). Odds ratios (ORs) and confidence intervals (CIs) were calculated to estimate the association between ACEs and sleep duration, adjusting for age, sex, and income. Results Of 32,959 participants (mean age 52.9 years), 18,901 (57%) reported at least one ACE, 62% identified as Black, and 46% had income &amp;lt;$15,000/year. Compared to zero ACE exposure, exposure to at least one ACE was associated with short (1.19 [1.13, 1.25]) and long (1.15 [1.06, 1.24]) sleep at baseline. Individuals with 4 or more ACEs were 1.32 times more likely to report short sleep than those without ACEs (1.23, 1.42). Abuse-related ACEs were associated with lower odds of short sleep (0.84 [0.74, 0.94]), while ACEs related to household dysfunction were associated with increased odds of short (1.22 [1.16, 1.28]) and long sleep (1.16 [1.07, 1.25]). Conclusion Among over 30,000 predominately low-income adults in the southeastern US, ACE exposure was associated with short and long sleep in adulthood. Greater ACE exposure (4+) was associated with greater odds of short sleep than lower ACE exposure. This pattern could reflect a trend toward shorter sleep with increasing ACEs. Further research should work to identify mechanisms connecting ACEs and abnormal sleep duration. Support (if any) Research was supported by the National Cancer Institute of the National Institutes of Health under Award Number U01CA202979. SCCS data collection was performed by the Survey and Biospecimen Shared Resource which is supported in part by the Vanderbilt-Ingram Cancer Center (P30 CA68485).