Weekday Bedtime Research Articles

Abstract P316: Sleep Timing Correlates With Incident Congestive Heart Failure: A Community-based Cohort Study

Introduction: Previous studies have suggested that sleep habits were associated with cardiovascular risk factors. However, there is no evidence about the relationship between sleep timing and congestive heart failure (CHF). Hypothesis: We assessed the hypothesis that the bedtime and wake-up time on weekday and weekend may be associated with incident CHF. Methods: From the Sleep Heart Health Study (registration number, NCT00005275), participants without previous heart failure were enrolled in the present prospective study. Sleep timing including bedtime and wake-up time on weekday and weekend was acquired from a self-reported Sleep Habits Questionnaire. Bedtime on weekdays and weekend was divided into >24:00, 23:01 to 24:00, 22:01 to 23:00 and ≤22:00. Wake-up time on weekdays and weekend was classified as >8:00, 7:01 to 8:00, 6:01 to 7:00 and ≤6:00. Further subgroup analysis was conducted according to sleep duration of <6h, 6-8h and >8h. Participants were followed up until the first CHF diagnosed between the date of the completed questionnaire and the final censoring date. Cox regression analysis was used to investigate the association between sleep timing and CHF. Results: A total of 4765 participants including 2207 males and 2558 females with a mean age of 63.6±11.0 years were recruited in the study. During the mean follow-up period of 11 years, 519 participants were diagnosed with CHF. The incidence of CHF in participants with weekday bedtime at >24:00 was 15.6% (69 of 441), which is higher than those with bedtime at 23:01 to 24:00 [12.7% (166 of 1306)], 22:01 to 23:00 [7.0% (128 of 1837)], and ≤22:00 [13.2% (156 of 1181)]. Participants with wake-up time on weekday at > 8:00 also had the highest incidence of CHF [19.7% (45 of 229)] than those with wake-up time at 7:01 to 8:00 [14.2% (89 of 627)], 6:01 to 7:00 [11.5% (171 of 1485)], and ≤6:00 [8.8% (214 of 2424)]. After multivariate Cox regression analyses, individuals with bedtime at >24:00 on weekdays was associated with a higher incidence of CHF (HR 1.559, 95% CI 1.151-2.113, P = 0.004) than those with bedtime at 22:01 to 23:00. And compared with participants with wake-up time at ≤6:00, those with wake-up time at > 8:00 also had an increased risk of incident CHF (HR 1.525, 95% CI 1.074-2.166, P =0.018). After further subgroup analysis, the association between bedtime at >24:00 on weekdays and incident CHF were strengthened in the participants with 6-8 hours’ sleep duration (HR 2.087, 95% CI 1.446-3.013, P <0.001). Conclusion: In conclusion, late bedtime (>24:00) and late wake-up time (>8:00) on weekdays may correlate with an increased risk of CHF. The impact of sleep timing on incident cardiovascular diseases may be worth further prospective study.

Bedtimes and Blood Pressure: A Prospective Cohort Study of Mexican Adolescents.

Hypertension affects up to 5% of children worldwide and predicts later cardiovascular morbidity. Associations of short sleep and hypertension have been frequently reported in adults but less consistently in children. This study aims to examine the role of late bedtimes, a marker of short sleep duration, and potentially misaligned circadian rhythms, on incident elevated blood pressure (BP) in a large cohort of Mexican children. Participants included 2,033 adolescents recruited from public schools in Morelos, Mexico, free from elevated BP (<90th sex, age, and height-standardized percentile). Fourteen months later, all adolescents had a second BP assessment. We abstracted baseline habitual bedtimes from questionnaires to evaluate the association between bedtime and elevated BP incidence (≥90th percentile). Risk ratios and 95% confidence intervals were estimated with discrete-time mixed survival models, adjusting for potential confounders and accounting for clustering by school. Participants were 12.5 (SD = 0.6) years old at baseline. At the follow-up visit 10% of adolescents had developed elevated BP. Compared to participants with a habitual weekday bedtime between 9 and 10 pm, those with a weekday bedtime 11 pm or later had a 1.87 times higher risk of developing elevated BP over the follow-up period (95% CI = 1.09, 2.21), after accounting for confounders. Participants with earlier weekday bedtimes also had a higher risk of elevated BP (RR = 1.96; 95% CI = 1.27, 3.01). The associations persisted after accounting for wake time. These data showed a U-shaped association between weekday bedtime and elevated/high BP risk among Mexican adolescents.

Association Between Late Bedtime and Diabetes Mellitus: A Large Community-Based Study.

The aim of this study was to investigate the association of bedtime with the prevalence of diabetes mellitus (DM) based on a large community-based population. In total, 5,420 participants (2,574 males and 2,846 females; aged 63.5 ± 11.0 years) from the Sleep Heart Health Study database were selected in this study. Sleep habit was recorded based on a questionnaire administered to patients upon recruitment. Bedtime was categorized as 11:00 pm and before, 11:00 pm to 12:00 am, and 12:00 am and later in the current study. Multivariate logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) to determine the relationship between bedtime and the prevalence of DM. The distribution of weekday bedtime at 11:00 pm and before, 11:00 pm to 12:00 am, 12:00 am and later was observed in 3,316 participants (61.2%), 991 participants (18.3%), and 1,113 participants (20.5%), respectively. Meanwhile, individuals with weekday bedtime of 12:00 am and later had a higher prevalence of DM than those with bedtime at 11:00 pm to 12:00 am, and 11:00 pm and before (10.6% versus 5.7% versus 6.6%, respectively; P < .001). In the adjusted multivariate logistic regression model, bedtime at 12:00 am and later on a weekday was significantly associated DM prevalence (OR 1.446, 95% CI 1.107-1.888, P = .007). No significant association was found between weekend bedtime and DM. Late bedtime at 12:00 am and later on a weekday may be a risk factor for the prevalence of DM. Stable sleep timing leads to lower risk of DM deserves future exploration.

Adolescent sleep and technology-use rules: results from the California Health Interview Survey

ObjectivesThis study reports on adolescent sleep, technology-use rules at home, and their potential association using the 2017 California Health Interview Survey (CHIS). MethodsCHIS cross-sectional, representative survey data was collected between June-December 2017 via telephone. Weekday bedtimes, rise times, and night time in bed in the past week, as well as whether technology-use rules were implemented at home, were examined among 448 adolescent residents of California (mean age = 14.5, range = 12-17; 48% women). ResultsThe average weekday nightly time in bed was 9.04 hours among 12- to 13-year-olds and 7.89 hours among 14- to 17-year-olds. The majority reported having technology-use rules and those who did, spent 35 more minutes in bed. Although a significant relationship was found between having technology-use rules and earlier bedtime, one was not found for time in bed, when controlling for demographics. ConclusionsMany California adolescents do not meet recommended sleep guidelines. Yet, technology-use rules appear to be associated with earlier bedtime. Results have implications for policy-making and adolescent sleep interventions.

Sleep & Circadian Health are Associated with Mood & Behavior in Adolescents with Overweight/Obesity

ABSTRACT Objective/Background Rates of overweight/obesity and insufficient/delayed sleep are high among adolescents and are also unique risk factors for mood/behavior difficulties. This study aimed to evaluate relationships between sleep/circadian health and mood/behavior in a cohort of adolescents with overweight/obesity. Participants Twenty-two adolescents (16.4 ± 1.1 years) with overweight/obesity attending high school completed in the study. Methods Participants completed one week of home sleep monitoring (actigraphy), questionnaires assessing chronotype (diurnal preference; Morningness/Eveningness Scale for Children) and mood/behavior (Strengths & Difficulties Questionnaire), and had in-laboratory salivary melatonin sampling on a Thursday or Friday during the academic year. Results Linear regressions revealed later weekday bedtime and shorter weekday time in bed and sleep duration were associated with worse mood/behavior scores. Shorter duration of melatonin secretion and greater “eveningness” were also associated with worse mood/behavior scores. Conclusions Short and late sleep, shorter melatonin secretion, and eveningness chronotype are associated with worse mood/behavior symptoms in a cohort of adolescents with overweight/obesity. Clinicians should assess for both sleep and mood/behavior symptoms and further research is needed to evaluate the impact of improved sleep on mood/behavior in adolescents with overweight/obesity.

Too Late and Not Enough: School Year Sleep Duration, Timing, and Circadian Misalignment Are Associated with Reduced Insulin Sensitivity in Adolescents with Overweight/Obesity

To examine the relationship between insulin resistance (IR) and sleep/circadian health in overweight/obese adolescents. We hypothesized that insufficient and delayed sleep would be associated with IR in this population. Thirty-one adolescents (mean age, 16.0 ± 1.4 years; 77% female) with body mass index ≥90th percentile for age/sex were recruited from outpatient clinics at a children's hospital. Participants underwent 1 week of objective home sleep monitoring with wrist actigraphy during the academic year. A 3-hour oral glucose tolerance test was conducted, followed by in-laboratory salivary dim-light melatonin sampling every 30-60 minutes from 5 p.m. to noon the next day. Regression analyses between sleep and circadian variables with IR were examined. Longer sleep time and time in bed on weekends and weekdays and earlier weekday bedtime were significantly associated with better insulin sensitivity. Participants who obtained less than the median duration of sleep per night (6.6 hours) had evidence of IR with compensatory insulin secretion compared with those obtaining ≥6.6 hours of sleep. A wider phase angle between bedtime and melatonin onset, indicating a later circadian timing of sleep onset, was significantly associated with IR. Short sleep duration, later weekday bedtime, and later circadian timing of sleep were associated with IR in a cohort of adolescents with overweight/obesity during the school year. Further research is needed to better understand the physiology underlying these observations and to evaluate the impact of improved sleep and circadian health on metabolic health in this at-risk population.

Sleep duration, timing, variability and measures of adiposity among 8- to 12-year-old children with obesity.

SummaryObjectivesSleep disruption in laboratory studies increases adiposity and decreases glucose tolerance. However, few epidemiological studies have used objective measures of sleep. This study aims to assess associations between sleep duration, timing and regularity with measures of adiposity.MethodsThis is a cross‐sectional study of 188 children with obesity (age: 10.50 ± 1.39 years; body mass index: 29.24 ± 5.04 kg m−2). Nightly sleep duration, bedtime and wake time were measured by multiple‐day actigraphy and parent reports. Per cent overweight (per cent over median body mass index for age and sex) was chosen as the primary measure of obesity status. Objective measures of height, weight, waist circumference, blood pressure, fasting blood lipids, glucose, insulin, glycated haemoglobin and C‐reactive protein were obtained. Television screen time and total caloric intake were assessed via parent questionnaire.ResultsEach hour later in weekday bedtime was associated with an additional 6.17 per cent overweight (95% confidence interval [CI]: 1.42–10.92). Each hour greater in day‐to‐day variability in weekday bedtime and weekday wake time was associated with an additional 10.20 (95% CI: 0.50–19.91) and 10.02 (95% CI: 1.55–18.50) per cent overweight, respectively. Associations were similar after controlling for other obesity‐related behaviours (television screen time, total caloric intake and physical activity.)ConclusionsAmong children with obesity, later bedtime and greater variability in bedtime and wake time are associated with greater adiposity, independent of other obesity‐related behaviours. Early bedtime and wake time and consistent day‐to‐day sleep timing may be strategies to reduce adiposity in high‐risk children.

Influence of Race, Ethnicity, and Behavioral Factors on Childhood Obesity

Childhood obesity is a public health concern resulting from a variety of reasons. In the United States, approximately 12.7 million children and adolescents are classified as obese. 23.8% of African American children are obese compared with 13.1% of whites between ages 6 to 11 years. In Alabama, 35.5% children are overweight and obese; it is 6th highest ranked in United States. The most common causes of childhood obesity are behavioral, genetic factors, or a combination of both. In this study we investigated the differences in some of the behavioral factors such as sleeping time, dinner time and television watching time in racial ethnic groups. 24 white/European American (EA) and 30 black/African American (AA) elementary school children aged between 6 to 10 years participated in this study. Height and weight were measured, without shoes and wearing only light clothing. Body mass index (BMI) percentile was calculated using Centers for Disease Control and Prevention growth reference. Parents reported child’s typical weekday bedtime, dinner time and television watching time of their children. 35% of EA children slept later than 8:30 pm during school days compared to 68% of AA children. Only 4% of EA children had late dinner (after 7 pm), whereas 50% of AA children had late dinner during week days. 21% of EA children watched television for more than 1 hour in comparison to 79% of AA children every day. Our findings suggest that insufficient sleep, late dinner schedule, and longer television exposure are some of the behavioral factors that contribute to greater percentage of childhood obesity in AA than EA children. Disclosure P. Ayine: None. E.P. Parra: None. R.B. Jeganathan: None. G. Thangiah: None.

Sleep, Circadian Rhythms, and Risk Across Health Domains in Adolescents With an Evening Circadian Preference

Sleep and circadian rhythm changes during adolescence contribute to increased risk across emotional, behavioral, cognitive, social, and physical health domains. This study examines if sleep and dim light melatonin onset (DLMO) are related to greater risk in these 5 health domains. Participants were 163 (93 female, age = 14.7 years) adolescents with an evening circadian preference from a study funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Sleep and circadian measures included weekday total sleep time (TST), bedtime, and shut-eye time assessed via sleep diary, the Children’s Morningness–Eveningness Preferences scale, and DLMO. Health domains included self-reported emotional, cognitive, behavioral, social, and physical health. Later DLMO was significantly associated with shorter weekday TST, later weekday bedtime, and later weekday shut-eye time, as well as lower risk in the behavioral domain. At the trend level, later DLMO was related to fewer physical health problems. Earlier DLMO combined with a later bedtime, later shut-eye time, or shorter TST predicted greater risk in the cognitive domain. Later DLMO and shorter TST or a later bedtime predicted worse physical health. DLMO timing was not related to the emotional or social domain. There is evidence that a discrepancy between sleep behaviors and the endogenous circadian rhythm may be related to risk in the cognitive domain for adolescents with an evening circadian preference. Preliminary evidence also indicated that a delayed DLMO and shorter TST or a later bedtime may be related to vulnerability to physical health risk.

Pathway-based analysis of genome-wide association study of circadian phenotypes.

Sleepiness affects normal social life, which attracts more and more attention. Circadian phenotypes contribute to obvious individual differences in susceptibility to sleepiness. We aimed to identify candidate single nucleotide polymorphisms (SNPs) which may cause circadian phenotypes, elucidate the potential mechanisms, and generate corresponding SNP-gene-pathways. A genome-wide association studies (GWAS) dataset of circadian phenotypes was utilized in the study. Then, the Identify Candidate Causal SNPs and Pathways analysis was employed to the GWAS dataset after quality control filters. Furthermore, genotype-phenotype association analysis was performed with HapMap database. Four SNPs in three different genes were determined to correlate with usual weekday bedtime, totally providing seven hypothetical mechanisms. Eleven SNPs in six genes were identified to correlate with usual weekday sleep duration, which provided six hypothetical pathways. Our results demonstrated that fifteen candidate SNPs in eight genes played vital roles in six hypothetical pathways implicated in usual weekday bedtime and six potential pathways involved in usual weekday sleep duration.

Sleep Patterns and Quality Are Associated with Severity of Obesity and Weight-Related Behaviors in Adolescents with Overweight and Obesity.

Inadequate sleep duration, sleep patterns, and sleep quality have been associated with metabolic, circadian, and behavioral changes that promote obesity. Adolescence is a period during which sleep habits change to include less sleep, later bedtimes, and greater bedtime shift (e.g., difference between weekend and weekday bedtime). Thus, sleep may play a role in adolescent obesity and weight-related behaviors. This study assesses sleep duration, quality, and schedules and their relationships to relative weight and body fat percentage as well as diet, physical activity, and screen time in adolescents with overweight/obesity. Adolescents between 12 and 17 years old (n = 186) were weighed and measured, reported typical sleep and wake times on weekdays and weekends, and responded to questionnaires assessing diet, physical activity, and screen time habits. Controlling for sleep duration, later weekend bedtime and greater bedtime shift were associated with greater severity of overweight (β = 0.20; β = 0.16) and greater screen time use (β = 0.22; β = 0.2). Later bedtimes on the weekdays and weekends were associated with fewer healthy diet practices (β = -0.26; β = -0.27). In addition, poorer sleep quality was associated with fewer healthy diet habits (β = -0.21), greater unhealthy diet habits (β = 0.15), and less physical activity (β = -0.22). Sleep duration was not associated with any weight or weight-related behavior. Sleep patterns and quality are associated with severity of overweight/obesity and various weight-related behaviors. Promoting a consistent sleep schedule throughout the week may be a worthwhile treatment target to optimize behavioral and weight outcomes in adolescent obesity treatment.

The effect of chronotype (morningness/eveningness) on medical students' academic achievement in Sudan.

ObjectivesThere is increasing awareness about the effects of circadian misalignment on health and work. In the present study, we aimed to investigate the effects of chronotype on academic achievement among medical students.MethodsA cross-sectional comparative study was conducted among 140 medical students (64 who averaged an A grade and 76 who averaged a C grade) completing the clinical phase at the medical college of Omdurman University, Sudan. The participants were asked to sign a written informed consent and to keep a diary detailing their bedtime, wake-up time, sleep latency, and sleep duration during working days and weekends. Then, the participants were invited to respond to a questionnaire. The chronotype was calculated from the mid-sleep time during the weekend and sleep debt. Various sleep parameters were then compared between the two groups. A t-test and logistic regression analysis were used to test the statistical significance.ResultsThe medical students with average grades were more of the evening chronotype than the students with excellent grades (p < 0.05). Significant differences were found between the two groups regarding weekend bedtime, wake-up time, and sleep duration. In addition, significant differences were evident for weekday bedtime, sleep latency, and wake-up lag between weekdays and weekends. No differences were observed between the two groups during weekday wake-up time and sleep duration, chronotype between gender, and bedtime delay between weekdays and weekends (p > 0.05).ConclusionStudents whose average grade was a C were more likely to have a later bedtimes during weekdays and weekends, sleep more during weekends, and were more evening.

Relationship between parent knowledge of child sleep, and child sleep practices and problems: A pilot study in a children's hospital cohort.

To describe parent reports of sleep practices, and examine associations with parent knowledge of child sleep, and whether children's sleep practices differ between parents who underestimated, overestimated or accurately estimated children's sleep needs. Parents of children aged 2-12 years (n = 115) attending hospital inpatient or day wards were approached and asked to report child sleep routines, sleep problems, parent education, household income and parent knowledge of child sleep via questionnaire. Younger age was associated with earlier bedtimes and wake times, shorter sleep latencies, longer sleep durations and greater sleep problems (P < 0.05). Parents from higher income homes reported earlier bedtimes and wake times, shorter sleep latencies and fewer sleep problems (P < 0.05). Parents with higher education reported shorter sleep latencies (P < 0.05). Parents with greater knowledge about child sleep reported earlier weekday and weekend bedtimes (r s ≥ 0.26) and wake times (r s ≥ 0.21) and greater consistency between their child's weekend and weekday sleep routines (P < 0.05). In comparison with parents who correctly estimated their child's sleep needs: parents who underestimated reported later weekday bedtimes (on average, 46 min), and longer sleep latencies (17 min); parents who overestimated reported longer sleep latencies (22 min). These findings remained significant when controlling for child age (P < 0.05). Parents with increased sleep knowledge, higher incomes and higher levels of education were more likely to report earlier bedtimes, wake times and more consistent sleep routines for their children.

Abstract P210: Sleep Duration and Eating Behavior in Young Adults: Project EAT

Background: Short sleep duration appears to put adults at risk for excess energy intake and obesity; less is known specifically about how sleep quantity relates to eating patterns. Objectives: We tested the association between sleep duration and eating among young adults, a group especially vulnerable to suboptimal sleep. Methods: We used data from Project EAT-III, a cross-sectional study of 1,854 racially/ethnically diverse young adults aged 20-30 from the Minneapolis/St. Paul metropolitan area. The EAT survey assessed: average sleep duration (calculated via weekday and weekend bedtimes and wake times), breakfast skipping, fast food, energy drink, and sport drink consumption. A food frequency questionnaire queried intake of sugar-sweetened, sugar-free, and caffeinated beverages. Linear and logistic regression, adjusted for demographic and behavioral covariates, were used to model the relationship between sleep duration and dietary outcomes. In logistic models, post-estimation commands were used to calculate risk ratios. Results: In linear models, participants who slept &amp;lt; 7 hours per night (11.5%) consumed significantly more caffeinated beverages relative to those who slept 7-8 hours per night (Table). In logistic models, those who slept 8-9 hours a night (26.6%) and &amp;gt; 9 hours per night (25.8%) reported a lower risk (0.85 (95% CI 0.70-0.99) and 0.80 (95% 0.63-0.98), respectively) of sports drink consumption, compared to those who slept 7-8 hours a night. Intake of sugar sweetened beverages, sugar-free beverages, energy drinks, breakfast, and fast food did not differ significantly by sleep duration. Conclusions: Sleep duration was related to some eating behaviors associated with energy imbalance, but not all. The impact of sleep insufficiency during young adulthood, a pivotal period in the life course, may set lifelong trajectories that may increase cardiovascular risk. Sleep may be an important target to include in interventions and policies aimed at cardiometabolic risk management.

School start time and sleep in Canadian adolescents.

Insufficient sleep is a serious problem in adolescents and school start time is thought to be a key contributor. This study provided the first comprehensive assessment of school start times across Canada and examined whether school start times were associated with sleep duration and tiredness among adolescents. We collected information on school start times from 362 schools that participated in the 2013/2014 Health Behaviour in School-aged Children study. We calculated sleep duration from weekday bedtime and wake time reported by 29635 students (aged 10-18years). We classified weekday sleep as sufficient if it met national recommendations, and used data on self-reported tiredness at school in the morning. Random-effects regression models estimated the association of school start time with sleep duration, sleep sufficiency and tiredness. On average, schools started at 08:43hours. Students slept an average of 8:36h on weekdays and 69% met sleep duration recommendations, but 60% reported feeling tired in the morning. Every 10-min delay in school start time corresponded with 3.2 [95% confidence interval (CI): 2.0, 4.5] additional minutes of sleep, a 1.6% (95% CI: 0.5, 2.8) greater probability of sufficient sleep and a 2.1% (95% CI: 1.0, 3.2) smaller probability of feeling tired at school in the morning. Students from schools that started later slept longer, were more likely to meet sleep recommendations and were less likely to report feeling tired in the morning. The study adds weight to the mounting evidence that delaying school start time benefits adolescent sleep.

Impact of a modest delay in school start time in Hong Kong school adolescents

ObjectiveTo examine the effects of a modest delay (15 min) in school start time (SST) on adolescent sleep patterns, mood, and behaviors. MethodsTwo secondary schools in Hong Kong with a total of 1173 students (intervention: n = 617; comparison school n = 556) completed both baseline and follow-up questionnaires. School start time was delayed by 15 min, from 7:45 a.m. to 8:00 a.m., in the intervention school. The comparison school maintained their regular SST at 7:55 a.m. Students' sleep-wake patterns, daytime sleepiness, and mental and behavioral aspects were assessed by validated questionnaires before and after the intervention. ResultsStudents in the intervention school significantly delayed their weekday wake-up time (p < 0.001) and increased their total time in bed (p < 0.001) when compared to students in the comparison school. Both groups experienced a delay in their weekday bedtime. The students in the intervention school showed improved mental health [General Health Questionnaire (GHQ) score, p = 0.015], better prosocial behaviors (p = 0.009), better peer relationships (p < 0.001), greater attentiveness (p < 0.001), less emotional problems (p = 0.002), and less behavioral difficulties (p < 0.001) as measured by Strengths and Difficulties Questionnaire (SDQ). ConclusionsA modest delay (15 min) in school start time can increase adolescent sleep with corresponding improvement in mood and behaviors. Current findings have significant implications for education policy, suggesting that school administrators and policy makers should systematically consider delaying school start time to promote sleep and health among school-aged adolescents. Clinical trial registrationChiCTR-TRC-12002798. The trial protocol can be accessed at: http://www.chictr.org/en/proj/show.aspx?proj=3955.

Morningness–eveningness and sleep habits at school: a comparative study between Mexico and Spain

Morningness–eveningness and sleep habits relationship were studied between Mexican and Spanish adolescents. A total sample of 611 Mexican and Spanish adolescents (13–15 years old; 14.12 ± 0.75) participated in this comparative study and filled out the preferred timing of sleep and activity using item 19 of Morningness–Eveningness Questionnaire and reported sleep habits from open questions about typical bed and rise times during the weekdays and weekends. Spanish adolescents reported differences in sleep habits according to sex and chronotype, whereas Mexican adolescents only reported differences regarding chronotype on weekends. When country effect was analyzed, the most relevant result was the short sleep length on weekdays of Mexican adolescents (7:11 vs. 8:05), who reported earlier weekday rise time (6:11 vs. 7:15) but similar weekday bedtime (23:00 vs. 23:09) compared to Spanish adolescents. Sleep habits among Mexicans seem more influenced by a social factor related to school schedule than environmental factor related to latitude.

Bedtime in Preschool-Aged Children and Risk for Adolescent Obesity

To determine whether preschool-aged children with earlier bedtimes have a lower risk for adolescent obesity and whether this risk reduction is modified by maternal sensitivity. Data from 977 of 1364 participants in the Study of Early Child Care and Youth Development were analyzed. Healthy singleton-births at 10 US sites in 1991 were eligible for enrollment. In 1995-1996, mothers reported their preschool-aged (mean=4.7years) child's typical weekday bedtime, and mother-child interaction was observed to assess maternal sensitivity. At a mean age of 15years, height and weight were measured and adolescent obesity defined as a sex-specific body-mass-index-for-age ≥95th percentile of the US reference. One-quarter of preschool-aged children had early bedtimes (8:00 p.m. or earlier), one-half had bedtimes after 8:00 p.m. but by 9:00 p.m., and one-quarter had late bedtimes (after 9:00 p.m.). Children's bedtimes were similar regardless of maternal sensitivity (P=.2). The prevalence of adolescent obesity was 10%, 16%, and 23%, respectively, across early to late bedtime groups. The multivariable-adjusted relative risk (95% CI) for adolescent obesity was 0.48 (0.29, 0.82) for preschoolers with early bedtimes compared with preschoolers with late bedtimes. This risk was not modified by maternal sensitivity (P=.99). Preschool-aged children with early weekday bedtimes were one-half as likely as children with late bedtimes to be obese as adolescents. Bedtimes are a modifiable routine that may help to prevent obesity.

Sleep and academic performance in later adolescence: results from a large population-based study.

The aim of the current study was to assess the association between sleep duration and sleep patterns and academic performance in 16-19 year-old adolescents using registry-based academic grades. A large population-based study from Norway conducted in 2012, the youth@hordaland-survey, surveyed 7798 adolescents aged 16-19years (53.5% girls). The survey was linked with objective outcome data on school performance. Self-reported sleep measures provided information on sleep duration, sleep efficiency, sleep deficit and bedtime differences between weekday and weekend. School performance [grade point average (GPA)] was obtained from official administrative registries. Most sleep parameters were associated with increased risk for poor school performance. After adjusting for sociodemographic information, short sleep duration and sleep deficit were the sleep measures with the highest odds of poor GPA (lowest quartile). Weekday bedtime was associated significantly with GPA, with adolescents going to bed between 22:00 and 23:00hours having the best GPA. Also, delayed sleep schedule during weekends was associated with poor academic performance. The associations were somewhat reduced after additional adjustment for non-attendance at school, but remained significant in the fully adjusted models. In conclusion, the demonstrated relationship between sleep problems and poor academic performance suggests that careful assessment of sleep is warranted when adolescents are underperforming at school. Future studies are needed on the association between impaired sleep in adolescence and later functioning in adulthood.

Monitoring of Weekly Sleep Pattern Variations at Home with a Contactless Biomotion Sensor.

Many people find that their sleep is restricted or disturbed by social obligations, including work. Sleep phase delays can affect an individual’s circadian rhythms on the following day and cause daytime sleepiness and/or poor performance. In this study, to examine weekly variations in sleep patterns, we analyzed sleep data for seven-day periods (from Sunday to Saturday) that had been collected from 2914 subjects (aged 20–79 years) over a total of 24,899 subject-weeks using contactless biomotion sensors. On the weekend, the subjects’ mean sleep midpoint, bedtime, and wake-up time were delayed by 40, 26 and 53 min, respectively, compared with those seen on weekdays. In addition, on weekdays, the mean difference between the maximum and median sleep midpoint ranged from 35 to 47 min among the subjects in their 20 s–70 s. The weekend delay and weekday variation in the subjects’ sleep patterns tended to decrease with age. This study detected sleep pattern disturbances on both weekdays and weekends. The serial changes in weekday bedtimes detected in this study suggest that sleep habits are influenced by changes in the temporal patterns of social activities/duties. We need further study the advantages of getting extra sleep and the disadvantages of sleep pattern disturbances in daily lifestyle.