Objectively Measured Sleep Duration and Health-Related Quality of Life in Older Adults with Metabolic Syndrome: A One-Year Longitudinal Analysis of the PREDIMED-Plus Cohort.

The aim of our cross-sectional and longitudinal study is to assess the relationship between daytime and night-time sleep duration and health-related quality of life (HRQoL) in adults with metabolic syndrome after a 1-year healthy lifestyle intervention. Analysis of the data from 2119 Spanish adults aged 55-75 years from the PREDIMED-Plus study was performed. Sleep duration was assessed using a wrist-worn accelerometer. HRQoL was measured using the SF-36 questionnaire. Linear regression models adjusted for socioeconomic and lifestyle factors and morbidity were developed. In cross-sectional analyses, participants with extreme night-time sleep duration categories showed lower physical component summary scores in Models 1 and 2 [ß-coefficient (95% confidence interval) <6 h vs. 7-9 h: -2, 3 (-3.8 to -0.8); p = 0.002. >9 h vs. 7-9 h: -1.1 (-2.0 to -0.3); p = 0.01]. Participants who sleep less than 7 h a night and take a nap are associated with higher mental component summary scores [ß-coefficient (95% confidence interval) 6.3 (1.3 to 11.3); p = 0.01]. No differences between night-time sleep categories and 12-month changes in HRQoL were observed. In conclusion, in cross-sectional analyses, extremes in nocturnal sleep duration are related to lower physical component summary scores and napping is associated with higher mental component summary scores in older adults who sleep less than 7 h a night.

Daytime sleep duration during infancy as an indicator for cognitive development at school age: a prospective cohort study.

STUDY OBJECTIVES: The reduction in daytime sleep during early life is considered one of the indicators of the maturation of sleep patterns, which is closely associated with cognitive development. The current study aims to analyze the relationships between daytime sleep duration (DSD) during infancy and cognitive development at 6 and 10 years. METHODS: The study included 262 mothers with their newborns from the Shanghai Sleep Birth Cohort Study, spanning 11 follow-ups from 42 days to 10 years. Sleep parameters were assessed using parent-reported questionnaires at each follow-up, and cognitive development was evaluated with the Wechsler Intelligence Scale for Children, fourth edition at 6 and 10 years. RESULTS: Two distinct DSD trajectories in early childhood were identified: "typical DSD" (66.7%) and "infancy excessive DSD" (33.3%). Children in the "infancy excessive DSD" trajectory exhibited lower working memory scores than those in the "typical DSD" trajectory at 6 years (mean difference = 5.90, 95% confidence interval [1.83, 9.96], P = .005) and 10 years (mean difference = 4.37, 95% confidence interval [0.26, 8.48], P = .037). Additional analysis in a relatively homogeneous sample consistently showed correlations between DSD trajectories and working memory performance. No consistent significant differences were found in other domains of cognitive development. CONCLUSIONS: Excessive daytime sleep during infancy may serve as an early indicator for poor working memory at school age. These findings raise concerns about the long-term cognitive development of infants with excessive DSD. CITATION: Lin J, Jiang Y, Xiao X, et al. Daytime sleep duration during infancy as an indicator for cognitive development at school age: a prospective cohort study. J Clin Sleep Med. 2024;20(7):1069-1077.

Early nap cessation in young children as a correlate of language and psychosocial outcomes: Evidence from a large Canadian sample.

OBJECTIVES: Most children stop napping between 2 and 5years old. We tested the association of early nap cessation (ie, children who stopped before their third birthday) and language, cognition functioning and psychosocial outcomes. METHODS: Data were from a national, longitudinal sample of Canadian children, with three timepoints. Children were 0-to-1 year old at T1, 2-to-3 years old at T2, and 4-to-5 years old at T3. Early nap cessation was tested as a correlate of children's psychosocial functioning (cross-sectionally and longitudinally), cognitive function (longitudinally), and language skills (longitudinally). There were 4923 children (50.9% male; 90.0% White) and their parents in this study who were included in the main analyses. Parents reported on demographics, perinatal and developmental variables, child functioning, and child sleep. Children completed direct assessments of receptive language and cognitive ability. Nap cessation, demographic, and developmental-control variables were tested as correlates of cross-sectional and longitudinal outcomes using linear regression (with a model-building approach). RESULTS: Early nap cessation correlated with higher receptive language ability (ß = 0.059 ± 0.028) and lower anxiety (ß = -0.039 ± 0.028) at T3, after controlling for known correlates of nap cessation, nighttime sleep, and other sociodemographic correlates of the outcomes. Cognitive ability, hyperactivity-inattention, and aggression were not correlated with nap cessation. CONCLUSIONS: Early nap cessation is related to specific benefits (ie, better receptive language and lower anxiety symptoms). These findings align with previous research. Future research should investigate differences associated with late nap cessation and in nap-encouraging cultures, and by ethnicity.

The combined effects of napping and self-selected motivation music during warming up on cognitive and physical performance of karate athletes.

Introduction: It has been established that napping or listening to motivational music during warm-up is an effective strategy to enhance cognitive and physical performances. However, which could provide better enhancement warrants further investigation. This study aimed to examine the effect of a 30-min nap opportunity (N30), a warm-up with self-selected motivational music (WUMM), and the combination of N30 with WUMM (WUMM + N30) on cognitive and physical performances in karate athletes. Method: In a randomized order, 14 national-level male karate athletes performed four experimental sessions: control, N30, WUMM, and WUMM + N30. Simple (SRT) and choice (CRT) reaction times, selective attention, subjective sleepiness (ESS), mood state (POMS), countermovement jump (CMJ), and karate agility test (KAT) were evaluated before and after an all-out exhaustive task [i.e., the Karate Specific Test (KST)]. Ratings of perceived exertion (RPE) were measured immediately after the KST. Results: Compared to the control, all interventions improved cognitive outcomes, mood, and sleepiness. No effects on physical performances (CMJ and KAT) were found after N30. Compared to N30, WUMM + N30 improved SRT pre- and post-exercise (pre: p < 0.05, d = 0.72; post: p < 0.001, d = 0.14), CRT (pre: p < 0.001, d = 0.07; post: p < 0.001, d = 0.10), attention (pre: p < 0.05, d = 0.06; post: p < 0.01, d = 0.06), mood (pre: p < 0.001, d = 2.53; post: p < 0.001, d = 0.23), and decreased ESS scores (pre: p < 0.01, d = 1.41; post: p < 0.05, d = 1.18). However, there was no significant difference between WUMM and N30. KST performance was not affected by the experimental conditions. However, the KST-induced performance deficit in CMJ and KAT was smaller following WUMM + N30 compared to WUMM and N30. RPE scores were lower following WUMM + N30 and WUMM. Conclusion: These findings suggest that a combination of listening to self-selected motivational music during warm-up with a 30-min nap could be an effective strategy to enhance cognitive and physical performance decline caused by fatigue induced by exercise.

Is sleep captured during a standard daytime EEG sufficient to diagnose Electrical Status Epilepticus in Sleep.

Electrical Status epilepticus of sleep (SES) is an EEG pattern where there is significant activation of epileptiform activity in NREM sleep. A spike wave index (SWI) of > 80-85% is often labelled as typical SES. We aimed to explore if sleep during a standard daytime-EEG, as compared an overnight-EEG, was adequate to diagnose ESES. Ten children with daytime and overnight studies suggestive of SES were audited. SWI and Spike Wave Density (SWD) were calculated for 5-minute epochs of wake in the daytime and overnight study, as well daytime-EEG sleep and first and last NREM cycle in the overnight-EEG. SWI in daytime NREM was not significantly different from SWI in the first sleep cycle of the overnight study. SWI in the last sleep cycle was significantly lower than the first sleep cycle in the overnight-EEG. SWD was significantly higher in the first sleep cycle in the overnight-EEG than the daytime sleep and the last NREM cycle. SES may be diagnosed in NREM sleep from a daytime-EEG study. Larger studies are needed to explore the significance of the disparity between SWI and SWD in the first and last NREM cycles in the overnight study.

The association between daytime sleep and general obesity risk differs by sleep duration in Iranian adults.

BACKGROUND: Sleep duration and daytime napping and obesity are related to adiposity; however, it is not clear whether the association between daytime napping and adiposity measures can differ by sleep duration. AIM: To clarify the association between daytime napping and general and abdominal obesity based on sleep duration of participants. SUBJECTS AND METHODS: This cross-sectional study was conducted on 1,683 individuals (837 men and 846 women) aged ≥ 35 years. Height, weight and waist circumference (WC) were measured according to the standard protocols. Body mass index (BMI) was calculated. Self-reported sleep duration (in a 24-hour cycle) was recorded. The odds of general and abdominal obesity were compared between nappers and non-nappers, stratified by their sleep duration (≤ 6 h, 6-8 h, ≥ 8 h). RESULTS: The mean (SD) age of participants was 47.48 ± 9.35 years. Nappers with a short sleep duration (≤ 6 h) had greater BMI and higher risk for overweight/obesity compared with counterpart non-nappers after adjustment for potential confounders (OR = 1.61, 95% CI = 1.07-2.41). In subjects with moderate sleep duration (6-8 h), nappers had a tendency towards higher BMI in comparison with non-nappers (28.04 ± 0.25 vs. 26.93 ± 0.51 kg/m2; p = 0.05), however, no significant difference was observed for the risk of obesity. Daytime napping was not related to the risk of obesity in long sleepers. No significant association was observed for abdominal obesity measures. CONCLUSIONS: Daytime napping is associated with increased risk of overweight/obesity in short sleepers. However, in subjects with longer sleep duration, it is not related to the risk of overweight/obesity.

Cardiorespiratory changes associated with micro-arousals during naps.

The autonomic nervous system (ANS) and the central nervous system (CNS) interplay during sleep, particularly during phasic events such as micro-arousals, has been the subject of several studies. The underlying mechanisms of such relationship which remain unclear, specifically during daytime sleep, were partly investigated in this study. Napping polysomnography was performed on two occasions at least one week apart in 15 healthy subjects. The following cardiorespiratory variables were extracted from the recordings: tachogram, pulse transit time (PTT), pulse wave amplitude, respiratory cycle amplitude, and frequency. Two experts first detected micro-arousal events, then, cardiorespiratory variables were averaged by 30-s epochs over 2 min centered on the onset of the micro-arousals. We found that in the 30 s preceding the arousal events as detected on the electroencephalogram (EEG) recordings, there was a decrease in tachogram, pulse wave amplitude, and PTT values while the respiratory amplitude increased. These changes were more prominent in stage N2 and N3 sleep than in stage N1. The present findings provide new insights into the autonomic changes during the pre-arousal period in daytime naps, as all the variables investigated suggest a sympathetic physiological origin for the changes.

Measurement of bradykinesia and chorea in Huntington's Disease using ambulatory monitoring.

Objectives: The feasibility of measuring bradykinesia and chorea in Huntington's Disease using a wearable sensor system (Parkinson's Kinetigraph: PKG) developed for measuring bradykinesia and dyskinesia in Parkinson's Disease was assessed. Methods: Unified Huntington's Disease Rating Scales (UHDRS) and a PKG were obtained for 25 people with Huntington's Disease. Bradykinesia and Chorea Score were derived from relevant sub-scores of the UHDRS and compared with the PKG's bradykinesia and dyskinesia scores. The PKG's daytime sleepiness score was also used. Results: There was good correlation between Chorea Scores and the PKG's dyskinesia score (Pearson's ρ = 0.66). Correlation between the Bradykinesia Scores and the PKG's bradykinesia score was also good (Pearson's ρ = 0.51) in cases whose PKG scores were in the normal or bradykinetic range. The PKG's bradykinesia score of 23, which is in the higher range of control subjects, separated participants into those with Independence Score ≥ 80 or < 80 and a Functional Assessment (FAS) score ≥ 18 or < 18. The PKG's daytime sleep score was high in 44 % of participants, whose average time asleep was 21 % compared to 1.6 % in participants with a normal sleep index. Participants with high sleep scores were significantly more likely to have low Independence and TFC scores. Conclusions: Measures of bradykinesia and dyskinesia from clinical scales have acceptable correlations with those from the PKG. Continuous monitoring provides information about daytime sleep, which was associated with lower functional status. Further studies and larger sample sizes are required to confirm these findings and the utility of this measure in Huntington's Disease.

Regular, intermittent, and spontaneous: Patterns of preschool Children's nap behavior and their correlates.

BACKGROUND: Daytime sleep during the preschool years (i.e., 1-5-years-old) is characterized by high inter-child variability in several components of nap behavior, including nap duration, nap timing, and the proportion of sleep during daytime. We used an empirical approach to examine variations amongst children in these aspects of napping and investigated correlates of these components of nap behavior. METHODS: A large, nationally representative sample (N = 702) of Canadian parents completed an online survey, including a one-month retrospective report of their 1.5-5 year old's daytime and nighttime sleep behavior and other questionnaires. To understand patterns of children's nap behaviors we applied Latent Profile Analysis (LPA) to typical nap duration, typical timing of naps, frequency of naps, proportion of sleep during the daytime, and the proportion of naps which were spontaneous (i.e., child just fell asleep). Then, multinominal logistic regression was used to examine correlates of profile membership. RESULTS: Four profiles of children emerged: (1) regular nappers; (2) intermittent nappers; (3) spontaneous nappers; and (4) non-nappers. After controlling for demographic variables (e.g., child age, sex, ethnicity) and known correlates of napping behaviors (e.g., birthweight, nighttime sleep duration), profile membership was related to parents' beliefs about napping, parents' own nap behaviors, family functioning, and child nighttime sleep problems in a multinominal logistic regression. CONCLUSIONS: An empirical approach aided in understanding the inter-child variability in napping amongst preschool-age children. Parental beliefs about napping and the home environment were shown to be critical factors influencing this variability.

Daytime Napping and Cognitive Health in Older Adults: A Systematic Review.

BACKGROUND: Daytime napping may improve cognitive function in older adults. However, the association can be complicated by specific features of napping and the older adult's health. This systematic review aims to synthesize the current literature on napping and cognition in older adults and provide recommendations for future research and daytime sleep practice in older adults. METHODS: Systematic searches for relative research published between January 1995 and October 2022 were conducted at PubMed, MEDLINE, PsycINFO, and Google Scholar using keywords individually and in multiple combinations. Manual searches were performed to identify additional studies. All included studies were critically appraised by 2 authors. RESULTS: Thirty-five studies, including 23 observational and 12 intervention studies, were reviewed. Findings from observational studies suggest a possible inverted U-shaped association between napping duration and cognitive function: short and moderate duration of naps benefited cognitive health in older adults compared with both non-napping and long or extended napping. Findings from intervention studies suggest one session of afternoon napping might improve psychomotor function and working memory, although with some inconsistency. The effect of multiple nap sessions on cognition was inconclusive due to a limited number of studies. CONCLUSION: More rigorous research studies are needed to investigate what causes different patterns of daytime napping, the associations between these distinct patterns and cognitive function, and to determine whether interventions targeting napping patterns can improve cognition in older adults. In addition, future research needs to comprehensively assess daytime napping using a combination of measures such as sleep diary and actigraphy.

The effect of caffeine, nap opportunity and their combination on biomarkers of muscle damage and antioxidant defence during repeated sprint exercise.

To investigate the effect of 20 min nap opportunity (N20), 5 mg · kg-1 of caffeine (CAF) and their combination (CAF+N20) on the biochemical response (energetic biomarkers, biomarkers of muscle damage and enzymatic antioxidants) to the running-based anaerobic sprint test. Fourteen highly trained male athletes completed in a double-blind, counterbalanced and randomized order four test sessions: no nap with placebo (PLA), N20, CAF and CAF+N20. Compared to PLA, all treatments enhanced maximum and mean powers. Minimum power was higher [(mean difference) 58.6 (95% confidence interval = 1.31-116) Watts] after CAF and [102 (29.9-175) Watts] after CAF+N20 compared to N20. Also, plasma glucose was higher after CAF [0.81 (0.18-1.45) mmol · l-1] and CAF+N20 [1.03 (0.39-1.64) mmol · l-1] compared to N20. However, plasma lactate was higher [1.64 (0.23-3.03) mmol · l-1] only after N20 compared to pre-exercise, suggesting a higher anaerobic glycolysis during N20 compared to PLA, CAF and CAF+N20. Caffeine ingestion increased post-exercise creatine kinase with [54.3 (16.7-91.1) IU · l-1] or without napping [58.9 (21.3-96.5) IU · l-1] compared to PLA. However, superoxide dismutase was higher after napping with [339 (123-554) U · gHB-1] or without caffeine [410 (195-625) U · gHB-1] compared to PLA. Probably because of the higher aerobic glycolysis contribution in energy synthesis, caffeine ingestion resulted in better repeated sprint performance during CAF and CAF+N20 sessions compared to N20 and PLA. Caffeine ingestion resulted in higher muscle damage, and the short nap enhanced antioxidant defence with or without caffeine ingestion.

A thermometer circuit for hot temperature adjusts Drosophila behavior to persistent heat.

Small poikilotherms such as the fruit fly Drosophila depend on absolute temperature measurements to identify external conditions that are above (hot) or below (cold) their preferred range and to react accordingly. Hot and cold temperatures have a different impact on fly activity and sleep, but the circuits and mechanisms that adjust behavior to specific thermal conditions are not well understood. Here, we use patch-clamp electrophysiology to show that internal thermosensory neurons located within the fly head capsule (the AC neurons1) function as a thermometer active in the hot range. ACs exhibit sustained firing rates that scale with absolute temperature-but only for temperatures above the fly's preferred ∼25°C (i.e., "hot" temperature). We identify ACs in the fly brain connectome and demonstrate that they target a single class of circadian neurons, the LPNs.2 LPNs receive excitatory drive from ACs and respond robustly to hot stimuli, but their responses do not exclusively rely on ACs. Instead, LPNs receive independent drive from thermosensory neurons of the fly antenna via a new class of second-order projection neurons (TPN-IV). Finally, we show that silencing LPNs blocks the restructuring of daytime "siesta" sleep, which normally occurs in response to persistent heat. Our previous work described a distinct thermometer circuit for cold temperature.3 Together, the results demonstrate that the fly nervous system separately encodes and relays absolute hot and cold temperature information, show how patterns of sleep and activity can be adapted to specific temperature conditions, and illustrate how persistent drive from sensory pathways can impact behavior on extended temporal scales.

Age and Sex Differences in the Association of Sleep Duration and Overweight/Obesity among Chinese Participants Age above 45 Years: A Cohort Study.

OBJECTIVES: We aimed to evaluate the association between sleep duration and obesity and estimate the attributable risk of sleep in the China Health and Retirement Longitudinal Study surveys (CHARLS). METHODS: A total of 9061 adults aged 45 years above from CHARLS (2011-2015) were included. The main outcome of this study was incident overweight/obesity specific to general and abdominal obesity. Overweight/obesity was defined as BMI ≥ 23.0 (kg/m2) and BMI≥27.5 (kg/m2), respectively. Abdominal obesity was defined as waist circumference ≥90 cm for men and ≥80 cm for women. Self-reported sleep durations were obtained using a structured questionnaire. We assessed hazard ratios (HRs) and 95% confidence intervals (CIs) as well as the population attributable fraction (PAF) for associations between sleep duration and obesity. RESULTS: 986 and 606 participants were identified as overweight and general obesity respectively, 1253 experienced abdominal obesity events. In multivariable-adjusted models, participants with daytime sleep of 0-30 minutes and more than 30 minutes associated with 30% (HR: 0.70, 95% CI: 0.56-0.87) and 35% (HR: 0.65, 95% CI: 0.55-0.78) decreased incident overweight risk respectively compared to those having no daytime sleep, this association also found among females and middle-aged, not males or elderly. Similarly, 0-30 minutes (HR: 0.68, 95% CI: 0.48-0.96) and more than 30 minutes of daytime sleep (HR: 0.73, 95% CI: 0.59-0.91) were associated with a reduced risk of abdominal obesity, similar results also found among females and middle-aged. Compared with 7-9 hours of nocturnal sleep, people who slept 5-7 hours had a reduced risk of overweight (HR: 0.59, 95% CI=0.47-0.74),but not found in subgroups. The hazard role of long nocturnal sleep for abdominal obesity was only found among elderly (HR: 2.33, 95% CI=1.35-4.04) and males (HR: 2.24, 95% CI=1.17-4.29). Compared with moderate total sleepers (7-9hours/day), participants with short total sleep duration exhibited an elevated risk of overweight (HR: 1.13, 95% CI=1.00-1.28), this also found among middle-aged. The PAF for inadequate total sleep duration (<7 hours/day) was 10.77% for overweight individuals. CONCLUSIONS: Insufficient sleep duration was associated with an elevated risk of overweight only detected among middle-aged not elderly and other subgroups specific by age. The risks for abdominal obesity were increased for males and middle-aged with long nocturnal sleep. Daytime sleep may significantly reduce the risk of overweight and abdominal obesity in female and middle-aged individuals. The link between sleep duration and obesity requires further study.

Sleep Homeostasis and Night Work: A Polysomnographic Study of Daytime Sleep Following Three Consecutive Simulated Night Shifts.

PURPOSE: Millions of people work at times that overlap with the habitual time for sleep. Consequently, sleep often occurs during the day. Daytime sleep is, however, characterized by reduced sleep duration. Despite preserved time spent in deep NREM sleep (stage N3), daytime sleep is subjectively rated as less restorative. Knowledge on how night work influences homeostatic sleep pressure is limited. Therefore, we aimed to explore the effect of three consecutive simulated night shifts on daytime sleep and markers of sleep homeostasis. PATIENTS AND METHODS: We performed continuous EEG, EMG and EOG recordings in the subjects' home setting for one nighttime sleep opportunity, and for the daytime sleep opportunities following three consecutive simulated night shifts. RESULTS: For all daytime sleep opportunities, total sleep time was reduced compared to nighttime sleep. While time spent in stage N3 was preserved, sleep pressure at sleep onset, measured by slow wave activity (1-4 Hz), was higher than nighttime sleep and higher on day 3 than on day 1 and 2. Elevated EEG power during daytime sleep was sustained through 6 h of time in bed. Slow wave energy was not significantly different from nighttime sleep after 6 h, reflecting a less efficient relief of sleep pressure. CONCLUSION: Adaptation to daytime sleep following three consecutive simulated night shifts is limited. The increased homeostatic response and continuation of sleep pressure relief even after 6 h of sleep, are assumed to reflect a challenge for appropriate homeostatic reduction to occur.

Excessive Daytime Sleepiness and Sleep Quality and their Impact on Health-Related Quality of Life in People with Epilepsy: A study from Pakistan.

BACKGROUND: Epilepsy is one of the most common but manageable neurological disorder. The relation between epilepsy, sleep, and health-related quality of life (HRQoL) in culturally distinct environment of Pakistan remains unclear. The purpose of this study was to determine prevalence and predictors of excessive daytime sleepiness (EDS), poor sleep quality (SQ), and to analyze their association with HRQoL in people with epilepsy (PWE). METHODS: A study was conducted among PWE attending two tertiary care hospitals of Islamabad and Rawalpindi, Pakistan. The EDS, SQ, and HRQoL were evaluated by Urdu versions of Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), and Quality of Life in Epilepsy-31 (QOLIE-31). RESULTS: The study included 200 PWE and 51 healthy controls with mean (SD) ages of 33.1 ±â€¯13.9, 32.9 ±â€¯10.9, and a disease duration of 5.01 ±â€¯6.17, respectively. The majority of the respondents (n = 130, 65%) had poor seizure control, and most of these (n = 88, 68%) were on combination antiepileptic drug (AED) therapy. In comparison to controls, a higher number of PWE had EDS by ESS (score ≥ 11, 10% vs. 40%, p-value 0.00), and poor SQ by PSQI (score > 5, 9% vs. 71%, p-value 0.00). A multiple logistic regression analysis reveals that the factors significantly associated with EDS were: female gender; increasing age; seizure control; duration of epilepsy; and combination AED therapy. A second multiple binary logistic regression analysis suggests that factors significantly associated with poor SQ were: increasing age; female gender; poor seizure control; and combination therapy. The Hierarchical multivariate analysis suggests that poor seizure control, EDS, and poor SQ were significant predictors of low HRQoL. CONCLUSION: The findings suggest high prevalence of EDS and poor SQ in PWE in Pakistan. A significant negative association exists between sleep complaints and HRQoL. During routine clinical consultations, awareness about sleep hygiene practices must be provided to enhance HRQoL.

Daytime Sleep as Compensation for the Effects of Reduced Nocturnal Sleep on the Incidence of Hypertension: A Cohort Study.

PURPOSE: The role of sleep duration in the development of hypertension remains controversial. Little is known about the combined effects of nocturnal and daytime sleep. We assessed the association between total sleep duration and the development of hypertension in middle-aged and elderly Chinese adults. PATIENTS AND METHODS: Data were obtained from 3 waves of China Health and Retirement Longitudinal Study surveys. Middle-aged and elderly Chinese initially without hypertension were followed biennially from 2011 to 2015. Sleep duration was self-reported. Hypertension was defined as a systolic and/or diastolic blood pressure ≥ 140/90 (mmHg), the current use of anti-hypertensive medications or self-reported hypertension. RESULTS: Over 31,392 person-years of follow-up, 2682 of 10,176 participants developed hypertension. The multivariable adjusted hazard ratios (HR) (95% confidence intervals, 95% CI) for the development of hypertension between those with 0-30 minutes and ≥30 minutes daytime sleep vs those without daytime sleep were 0.67 (0.58, 0.77), and 0.73 (0.59, 0.92), respectively. The protective role of longer periods of daytime sleep (>30 minutes) varied between different subgroups. Compared with moderate nocturnal sleepers, long nocturnal sleepers (HR: 1.66, 95% CI=1.25-2.21) had an increased risk of hypertension. Compared with moderate nocturnal sleepers without daytime sleep, HRs (95% CI) for hypertension were 0.52 (0.45, 0.59) for short nocturnal sleep plus short daytime sleep and 0.55 (0.49, 0.62) for short nocturnal sleep plus long daytime sleep. People with extremely short (HR: 1.34, 95% CI=1.22-1.48) and long (HR: 1.28, 95% CI=1.13-1.44) combined sleep periods had an increased risk of hypertension. Consistent results were also found in subgroups stratified by age and gender. CONCLUSION: Both extremely long and short total sleep periods were associated with an increased risk of hypertension. People with short or moderate nocturnal sleep durations, especially short nocturnal sleep duration, can benefit from habitual daytime sleep to prevent hypertension.

Differences in Daytime Activity Levels and Daytime Sleep Between Night and Day Duty: An Observational Study in Italian Orthopedic Nurses.

Working nonstandard work schedules is often associated with increased sedentary behavior and risk of sleep disorders. Night shift workers are prone to accumulating sleep debt, which they recover by sleeping during the day. The effect on daytime activity levels is unknown. The present study aims to objectively assess whether daytime sleep could affect daytime activity levels of shift worker nurses, resulting in an accumulation of their activity debt differently between working and rest periods. The study population (N = 37; mean age 41.7 ± 9.1 years) was composed of orthopedic nurses working on a rotating schedule, including either a night shift (NS) or only day/afternoon shift (DS). Actigraph monitoring lasted both on the working and the rest period. For the NS nurses, the working period recorded higher daytime activity levels than the rest period, while daytime sleep during the working and rest periods was similar. Conversely, DS nurses showed higher daytime activity levels and shorter daytime sleep during the working period. NS nurses were less active than DS nurses during the working period, probably because NS tended to have a longer daytime sleep. During the rest period, daytime activity levels for both groups were decreased. For NS nurses, sleep recorded the better sleep parameters during the rest period, while sleep parameters did not show significant differences between the working and the rest periods in DS. During the working period, NS nurses slept worse than the DS nurses. Both groups tended to accumulate a debt in daytime activity levels during the rest period. While daytime sleep may be an excellent way to counteract sleep debt and increase sleep duration over 24 h period, on the other hand, it makes nurses less active.

Caffeine Use or Napping to Enhance Repeated Sprint Performance After Partial Sleep Deprivation: Why Not Both?

PURPOSE: To compare the effect of a 20-minute nap opportunity (N20), a moderate dose of caffeine (CAF; 5 mg·kg-1), or a moderate dose of caffeine before N20 (CAF+N) as possible countermeasures to the decreased performance and the partial sleep deprivation-induced muscle damage. METHODS: Nine male, highly trained judokas were randomly assigned to either baseline normal sleep night, placebo, N20, CAF, or CAF+N. Test sessions included the running-based anaerobic sprint test, from which the maximum (Pmax), mean (Pmean), and minimum (Pmin) powers were calculated. Biomarkers of muscle, hepatic, and cardiac damage and of enzymatic and nonenzymatic antioxidants were measured at rest and after the exercise. RESULTS: N20 increased Pmax compared with placebo (P < .01, d = 0.75). CAF+N increased Pmax (P < .001, d = 1.5; d = 0.94), Pmin (P < .001, d = 2.79; d = 2.6), and Pmean (P < .001, d = 1.93; d = 1.79) compared with placebo and CAF, respectively. Postexercise creatine kinase increased whenever caffeine was added, that is, after CAF (P < .001, d = 1.19) and CAF+N (P < .001, d = 1.36). Postexercise uric acid increased whenever participants napped, that is, after N20 (P < .001, d = 2.19) and CAF+N (P < .001, d = 2.50) and decreased after CAF (P < .001, d = 2.96). CONCLUSION: Napping improved repeated-sprint performance and antioxidant defense after partial sleep deprivation. Contrarily, caffeine increased muscle damage without improving performance. For sleep-deprived athletes, caffeine before a short nap opportunity would be more beneficial for repeated sprint performance than each treatment alone.

[Effects of weak low-frequency electromagnetic field on sleep structure during daytime sleep]. / Vliyanie ekspozitsii slabogo elektromagnitnogo polya sverkhnizkoi chastoty na strukturu dnevnogo sna.

OBJECTIVE: To test the hypothesis that weak electromagnetic fields of low frequencies (0.5-26 Hz) could affect daytime sleep features and structure. MATERIAL AND METHODS: Parameters of daytime sleep continuity were compared in the study with counterbalanced control/exposition (40 min exposure to electromagnetic field at 1 Hz/0.004 µT) scheme in 22 healthy volunteers. Nonlinear regression model was used to assess daytime sleep continuity. RESULTS: Exposure to a weak electromagnetic field of ultra-low frequency significantly improved the quality of sleep, assessed by the indicator of sleep continuity, namely, there were fewer transitions from the second and deeper stages of sleep to the first stage and to the state of wakefulness (p<0.0001). CONCLUSION: The results can be used to develop non-pharmacological methods of sleep correction, as well as to improve the quality of short-term sleep and its positive effect on well-being, cognitive function and working capacity.

Variability of Sleep and Relations to Body Weight Among First-Year College Students.

BACKGROUND: Existing research suggests that greater sleep variability may increase risk for weight gain. College often marks a transition to a less consistent daily schedule, which may adversely impact sleep routines and further increase risk for weight gain. The current study is among the first to explore relations between nighttime sleep variability and daytime sleep (napping) and body weight among first-year college students. METHODS: Using daily diary methods, first-year college students (N = 307; 84.7% female) self-reported their sleep for seven days. Several indices were created to capture sleep variability for reported bedtime, wake time, and sleep duration, including weekday versus weekend differences (WvW), day to day differences (D2D), and overall standard deviation (SD). Napping was also assessed. Based on body mass index (BMI), individuals were categorized as underweight, healthy weight, overweight, and obese. RESULTS: Across indices, students' sleep varied over an hour on average across the week. Hierarchical regressions revealed that greater differences in wake time D2D, wake time SD, and sleep duration WvW were all associated with higher BMI, after accounting for gender, depressive symptoms, and sleep duration. Longer napping was also associated with higher BMI, using the same covariates. Finally, greater sleep variability was reported by overweight and obese than healthy weight individuals. CONCLUSION: These findings suggest that sleep variability, particularly wake times and napping may be important modifiable sleep behaviors to investigate in future studies. More longitudinal research is needed to explore relations between multiple facets of sleep variability and weight gain, including possible mechanisms.