Differences in sleep and circadian preference between Eastern and Western German adolescents

Only a few studies focus on comparisons to reveal differences in sleep and circadian preferences in adolescents. This study used the same instrument to compare adolescents in Eastern and Western Germany. In all, 674 pupils between 11 and 16 yrs participated. The questionnaire asked questions about wake times and bed times (on weekend and weekdays), and the Composite Scale of Morningness (CSM) was completed to assess diurnal preferences. Locality (East/West Germany) had no effect on rise and bed times during the week and on sleep length on the weekend. Western pupils rose later on weekends and went to bed later on weekends. While sleep length on weekdays was shorter in West Germany, weekend oversleep was longer and misalignment was higher. Diurnal preferences (CSM scores) suggested a higher eveningness in West Germany. As interaction effects were insignificant, changes throughout adolescence seem similar in East and West Germany. These data suggest that given similar school start times, Western German pupils are at higher risk because they are later chronotypes. The finding of earlier rise and bed times of the East German pupils is consistent with the hypothesis that sunlight acts as the entrainment for the biological clock of adolescents, as sunrise is earlier in Eastern Germany.     

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.     

MODIFICATIONS TO WEEKEND RECOVERY SLEEP DELAY CIRCADIAN PHASE IN OLDER ADOLESCENTS

Adolescents often report shorter time in bed and earlier wake-up times on school days compared to weekend days. Extending sleep on weekend nights may reflect a “recovery” process as youngsters try to compensate for an accumulated school-week sleep debt. The authors examined whether the circadian timing system of adolescents shifted after keeping a common late weekend “recovery” sleep schedule; it was hypothesized that a circadian phase delay shift would follow this later and longer weekend sleep. The second aim of this study was to test whether modifying sleep timing or light exposure on weekends while still providing recovery sleep can stabilize the circadian system. Two experiments addressed these aims. Experiment 1 was a 4-wk, within-subjects counterbalanced design comparing two weekend sleep schedule conditions, “TYPICAL” and “NAP.” Compared to weeknights, participants retired 1.5?h later and woke 3?h later on TYPICAL weekends but 1?h later on NAP weekends, which also included a 2-h afternoon nap. Experiment 2 was a 2-wk, between-subjects design with two groups (“TYPICAL” or “LIGHT”) that differed by weekend morning light exposure. TYPICAL and LIGHT groups followed the TYPICAL weekend schedule of Experiment 1, and the LIGHT group received 1?h of light (454–484?nm) upon weekend wake-up. Weekend time in bed was 1.5?h longer/night than weeknights in both experimental protocols. Participants slept at home during the study. Dim light melatonin onset (DLMO) phase was assessed in the laboratory before (Friday) and after (Sunday) each weekend. Participants were ages 15 to 17 yrs. Twelve participants (4 boys) were included in Experiment 1, and 33 (10 boys) were included in Experiment 2. DLMO phase delayed over TYPICAL weekends in Experiment 1 by (mean?±?SD) 45?±?31?min and Experiment 2 by 46?±?34?min. DLMO phase also delayed over NAP weekends (41?±?34?min) and did not differ from the TYPICAL condition of Experiment 1. DLMO phase delayed over LIGHT weekends (38?±?28?min) and did not differ from the TYPICAL group of Experiment 2. In summary, adolescents phase delay after keeping a commonly observed weekend sleep schedule. Waking earlier or exposure to short-wavelength light on weekend mornings, however, did not stabilize circadian timing in this sample of youngsters. These data inform chronotherapy interventions and underscore the need to test circadian phase-shifting responses to light in this age group. (Author correspondence: Stephanie_J_Crowley@rush.edu)     

Relationships among sleep timing,sleep duration and glycemic control in Type 2 diabetes in Thailand

There is evidence that the sleep and circadian systems play a role in glucose metabolism. In addition to physiological factors, sleep is also affected by behavioral, environmental, cultural and social factors. In this study, we examined whether morning or evening preference, sleep timing and sleep duration are associated with glycemic control in patients with type 2 diabetes residing in Thailand. Two hundred and ten type 2 diabetes patients who were not shift workers completed an interview and questionnaires to collect information on diabetes history, habitual sleep duration and sleep timing. Chronotype, an individual’s tendency for being a “morning” or “evening” person, was assessed using the Composite Score of Morningness (CSM), which reflects an individual’s subjective preference for activities in the morning or evening, as well as mid-sleep time on weekend nights (MSF), which reflects their actual sleep behavior. Most recent hemoglobin A1c (HbA1c) values were retrieved from medical records. Evening preference (as indicated by lower CSM), later bedtime on weekends, and shorter sleep duration correlated with higher HbA1c (r?=??0.18, p?=?0.01; r?=?0.17, p?=?0.01 and r?=??0.17, p?=?0.01, respectively), while there was no association between MSF or wake up time and glycemic control. In addition, later bedtime on weekends significantly correlated with shorter sleep duration (r?=??0.34, p?<?0.001). Hierarchical regression analyses adjusting for age, sex, body mass index, insulin use and diabetes duration revealed that later bedtime on weekends was significantly associated with poorer glycemic control (B?=?0.018, p?=?0.02), while CSM was not. Mediation analysis revealed that this association was fully mediated by sleep duration. In summary, later bedtime on weekends was associated with shorter sleep duration and poorer glycemic control in patients with type 2 diabetes. It is likely that patients with later weekend bedtimes curtail their sleep by waking up earlier. Exploring the potential reasons for this phenomenon (e.g. cultural influences, metropolitan lifestyle, environmental factors, family and social obligations) specific to a Thai population may help identify behavioral modifications (i.e. earlier bedtime and/or sleep duration extension) that could possibly lead to improved glycemic control in this population.     

Differences in circadian phase and weekday/weekend sleep patterns in a sample of middle-aged morning types and evening types

Factors contributing to sleep timing and sleep restriction in daily life include chronotype and less flexibility in times available for sleep on scheduled days versus free days. There is some evidence that these two factors interact, with morning types and evening types reporting similar sleep need, but evening types being more likely to accumulate a sleep debt during the week and to have greater sleep extension on weekend nights. The aim of the present study was to evaluate the independent contributions of circadian phase and weekend-to-weekday variability to sleep timing in daily life. The study included 14 morning types and 14 evening types recruited from a community-based sample of New Zealand adults (mean age 41.1 ± 4.7 years). On days 1–15, the participants followed their usual routines in their own homes and daily sleep start, midpoint and end times were determined by actigraphy and sleep diaries. Days 16–17 involved a 17 h modified constant routine protocol in the laboratory (17:00 to 10:00, <20 lux) with half-hourly saliva samples assayed for melatonin. Mixed model ANCOVAs for repeated measures were used to investigate the independent relationships between sleep start and end times (separate models) and age (30–39 years versus 40–49 years), circadian phase [time of the dim light melatonin onset (DLMO)] and weekday/weekend schedules (Sunday–Thursday nights versus Friday–Saturday nights). As expected on weekdays, evening types had later sleep start times (mean = 23:47 versus 22:37, p < .0001) and end times (mean = 07:14 versus 05:56, p < .0001) than morning types. Similarly on weekend days, evening types had later sleep start times (mean = 00:14 versus 23:07, p = .0032) and end times (mean = 08:56 versus 07:04, p < .0001) than morning types. Evening types also had later DLMO (22:06 versus 20:46, p = .0002) than morning types (mean difference = 80.4 min, SE = 18.6 min). The ANCOVA models found that later sleep start times were associated with later DLMO (p = .0172) and weekend-to-weekday sleep timing variability (p < .0001), after controlling for age, while later sleep end times were associated with later DLMO (p = .0038), younger age (p = .0190) and weekend days (p < .0001). Sleep end times showed stronger association with DLMO (for every 30 min delay in DLMO, estimated mean sleep end time occurred 14.0 min later versus 10.19 min later for sleep start times). Sleep end times also showed greater delays on weekends versus weekdays (estimated mean delay for sleep end time = 84 min, for sleep start time = 28 min). Comparing morning types and evening types, the estimated contributions of the DLMO to the mean observed differences in sleep timing were on weekdays, 39% for sleep start times and 49% for sleep end times; and on weekends, 41% for sleep start times and 34% of sleep end times. We conclude that differences in sleep timing between morning types and evening types were much greater than would be predicted on the basis of the independent contribution of the difference in DLMO on both weekdays and weekend days. The timing of sleep in daily life involves complex interactions between physiological and psychosocial factors, which may be moderated by age in adults aged 30–49 years.     

Sleep-Wake Cycle of Adolescents in Côte d'Ivoire: Influence of Age,Gender, Religion and Occupation

The human sleep-wake cycle is characterized by significant individual differences. Those differences in the sleep-wake cycle are partially heritable but are also influenced by environmental factors like the light/dark cycle or social habits. In this study we analyse for the first time the sleep-wake rhythm of adolescent pupils and working adolescents in a less industrialised country in West Africa near the equator. The aim of this study was to explore the sleep wake cycle in this geographical region, using Côte d'Ivoire as an example. Data collection took place between 2nd of March and 10th of June 2009. 588 adolescents (338 girls, 250 boys) between 10 and 15 years (mean?±?SD: 12.72?±?1.63) participated in this study. We collected data on the religion of the participants (Christian (N?=?159), Muslim (N?=?352), other/no religion (N?=?77)) and their occupation. Participants were either pupils attending school (N?=?336) or adolescents that were already working (N?=?252) and not attending school. The interviewer filled in the questionnaire. We found significant effects of age (p?<?0.001), gender (p?<?0.001), occupation (p?=?0.002), religion (p?<?0.001) and region (p?<?0.001). The midpoint of sleep was on average 1:26 (SD: 00:30) on weekdays and 1:37 (SD: 00:42) on weekend days. There are significant differences between weekdays and weekend days, but these were only small. Sleep duration suggests that adolescents in Côte d'Ivoire may gain sufficient sleep during week and weekend days, and thus, may live more in accordance with their own biological clock than adolescents in the northern hemisphere. In contrast, the data can be interpreted that adolescents live in a permanent ‘jetlag’. Factors may be the more continuous light/dark cycle in the tropics, low amount of ambient light and less electricity.     

Eveningness, sleep patterns, daytime functioning, and quality of life in Israeli adolescents

The purpose of the study was to assess the relationships between eveningness, sleep patterns, measures of daytime functioning, i.e., sleepiness, sleep problem behaviors, and depressed mood, and quality of life (QOL) in young Israeli adolescents. A cross-sectional survey was performed in urban and rural middle schools in Northern Israel. Participants were 470 eighth and ninth grade middle school students (14?±?0.8 yrs of age) in the normative school system. Students completed the modified School Sleep Habits Survey (SSHS) and Pediatric Quality of Life Inventory Short Form, assessing six subscales of physical, emotional, social, school performance, and psychosocial functioning, plus an addition generated total score. During weekdays and weekends, evening types went to bed later, their sleep latency was longer, their wake-up time was later, and their sleep duration was shorter than intermediate and morning types. Evening types exhibited more sleep problem behaviors, sleepiness, depressed mood, and lower QOL compared to intermediate and morning types. Based on the regression model, sleepiness, sleep-problem behaviors, and depressed mood were the variables most strongly associated with QOL, followed by morning-evening preference, weekday sleep duration, and weekend sleep latency. This study is the first to assess QOL in normative, healthy adolescents and to demonstrate strong associations between morning-evening preference and QOL. These findings enhance the need to identify young individuals with an evening preference, and to be aware of the characteristics and manifestations of the evening chronotype on daytime and nighttime behaviors in adolescence.     

Effects of Age and Gender on Sleep Habits and Sleep Trouble for Aged People

The healthy 455 subjects above 60 years of age were questioned on their sleep habit inventory and the morningness-eveningness questionnaire. We analyzed the effects of age and sex on sleep habits and sleep-related trouble. Bedtimes on weekdays and weekends became earlier with aging, and women went to bed significantly later than men did. The length of sleep on weekdays slightly increased with aging, and it was longer for men than for women. The number of urinations and awakenings during nocturnal sleep and the amount of daytime napping increased with aging. The score on morningness-eveningness shifted toward the morning type with aging. In comparison with men, women had significantly longer sleep latency; and a higher percentage of subjects who reported that they sleep for only a short time, have sleep trouble, have received medical treatment for their sleep trouble, and take sleep medication. From these results, we deduced that the phase of sleep shifted forward in subjects above 60 years of age, and they showed frequent interruptions during nocturnal sleep and long daytime napping. We discussed the factor of gender difference in sleep in relation to social and cultural factors, particularly the household activities of women.     

Effects of Age and Gender on Sleep Habits and Sleep Trouble for Aged People

The healthy 455 subjects above 60 years of age were questioned on their sleep habit inventory and the morningness-eveningness questionnaire. We analyzed the effects of age and sex on sleep habits and sleep-related trouble. Bedtimes on weekdays and weekends became earlier with aging, and women went to bed significantly later than men did. The length of sleep on weekdays slightly increased with aging, and it was longer for men than for women. The number of urinations and awakenings during nocturnal sleep and the amount of daytime napping increased with aging. The score on morningness-eveningness shifted toward the morning type with aging. In comparison with men, women had significantly longer sleep latency; and a higher percentage of subjects who reported that they sleep for only a short time, have sleep trouble, have received medical treatment for their sleep trouble, and take sleep medication. From these results, we deduced that the phase of sleep shifted forward in subjects above 60 years of age, and they showed frequent interruptions during nocturnal sleep and long daytime napping. We discussed the factor of gender difference in sleep in relation to social and cultural factors, particularly the household activities of women.     

Gender differences in sleep habits and quality and daytime sleepiness in elementary and high school teachers

The extensive workload of teachers inside and outside the classroom may contribute to sleep problems. Such problems may occur more frequently in women due to the combination of professional demands, domestic tasks, and their relatively greater sleep needs compared to men. The objective of this cross-sectional study was to evaluate the influence of gender on sleep habits and quality, and daytime sleepiness in a sample of 243 teachers (77 men and 166 women) using questionnaires. Linear regression models were used to examine the effect of gender on sleep measures; the unadjusted model considered only gender and the adjusted model considered chronotype and work characteristics as potential confounders. Bedtimes of women were significantly earlier than men during the week, but not on weekends, in the unadjusted and adjusted models. Time in bed was longer for women throughout the week and weekend in the unadjusted model. However, in the adjusted model, this statistical significance disappeared, and longer time in bed during the week was associated with teaching in one shift and for both levels of education. In addition, the female gender was associated with higher sleepiness scores compared to males in both models, and worse sleep quality in the adjusted model. Also, sleep quality was worse in subjects working in three shifts and in both types of schools (public and private). The tendency to eveningness was associated with later bedtimes and wake up times during both week days and weekends, higher irregularity of bedtimes and wake up times, and higher sleepiness scores in the adjusted model. Therefore, we suggest that female teachers do not fulfill their sleep needs and show higher levels of diurnal sleepiness and poor sleep quality that can be modulated by chronotype and some work characteristics. More studies are needed to evaluate the role of double workload on this pattern.     

Association of depressive symptoms with habitual sleep duration and sleep timing in junior high school students

ABSTRACT

This study aims to investigate independent associations of habitual sleep durations and sleep timings on weekdays and weekends with depressive symptoms in adolescents who have classes in the morning. We studied grade 7–9 students (942 males and 940 females, aged 12–15 years), who had classes in the morning, at public junior high schools in Japan in a cross-sectional design. The students answered a self-report questionnaire, which covers habitual sleep durations, bedtimes and wake-up times on weekdays and weekends, and depressive symptoms. The Short Mood and Feelings Questionnaire (SMFQ) was used to determine the level of depressive symptoms. The relationship between the variables on sleep habits and the SMFQ score were studied using multivariate linear regression and generalized additive models (GAM), controlling for sex, age and school. Multivariate linear regression analysis revealed that sleep duration on weekdays and relative mid-sleep time on weekdays (i.e. mid-sleep time on weekdays – mid-sleep time on weekends) were independently significantly (p < .001) associated with the SMFQ score. GAM analysis also revealed that sleep duration on weekdays (a reverse J-shaped relationship) and the relative mid-sleep time on weekdays (a negative monotonic/linear relationship) were independently significantly (p < .001) associated with the SMFQ score. These associations were confirmed in both males and females when they were analyzed separately. These results suggest that sleep duration on weekdays and the relative mid-sleep time on weekdays may be independently associated with the level of depressive symptoms in junior high school students who have classes in the morning. These findings may have important implications for the development of novel strategies for preventing mental health problems in adolescents.     

Sleep-Wake Patterns of Student Workers and Non-Workers

Adolescents usually exhibit late sleep phase and irregular sleep patterns. As a result, they do not get enough sleep and report daytime sleepiness. This condition could be aggravated in working students who have a more limited time for sleep. In this survey, we investigated the impact of evening classes and employment on the sleep patterns of adolescents. We compared female (n = 17) and male (n = 14) non-worker students to female (n = 28) and male (n = 20) worker students who attended the same high school. The volunteers (aged 17.4 years ± 11 months) answered a sleep log during a 16-day period. Worker students slept and woke up earlier, had a shorter nocturnal sleep length and a shorter daily (nocturnal plus diurnal) sleep length compared to non-working pupils. The four groups of students delayed sleep onset time on weekends, but only worker students delayed wake-up time on Sundays. The wake-up time was similar among groups on Sundays. While student workers tended to increase the sleep length in the weekends, non-working students increased it on Mondays and/or Tuesdays. The results showed that sleep schedules and sleep length were different according to the work status. Going to bed later on Saturday by the four groups of students suggests the influence of social activities, while a later wake-up time on Sundays could result from a shorter sleep length on workdays.     

Adolescent Sleep Patterns and Night-Time Technology Use: Results of the Australian Broadcasting Corporation's Big Sleep Survey

Introduction

Electronic devices in the bedroom are broadly linked with poor sleep in adolescents. This study investigated whether there is a dose-response relationship between use of electronic devices (computers, cellphones, televisions and radios) in bed prior to sleep and adolescent sleep patterns.

Methods

Adolescents aged 11–17 yrs (n = 1,184; 67.6% female) completed an Australia-wide internet survey that examined sleep patterns, sleepiness, sleep disorders, the presence of electronic devices in the bedroom and frequency of use in bed at night.

Results

Over 70% of adolescents reported 2 or more electronic devices in their bedroom at night. Use of devices in bed a few nights per week or more was 46.8% cellphone, 38.5% computer, 23.2% TV, and 15.8% radio. Device use had dose-dependent associations with later sleep onset on weekdays (highest-dose computer adjOR  = 3.75: 99% CI  = 2.17–6.46; cellphone 2.29: 1.22–4.30) and weekends (computer 3.68: 2.14–6.32; cellphone 3.24: 1.70–6.19; TV 2.32: 1.30–4.14), and later waking on weekdays (computer 2.08: 1.25–3.44; TV 2.31: 1.33–4.02) and weekends (computer 1.99: 1.21–3.26; cellphone 2.33: 1.33–4.08; TV 2.04: 1.18–3.55). Only ‘almost every night’ computer use (: 2.43: 1.45–4.08) was associated with short weekday sleep duration, and only ‘almost every night’ cellphone use (2.23: 1.26–3.94) was associated with wake lag (waking later on weekends).

Conclusions

Use of computers, cell-phones and televisions at higher doses was associated with delayed sleep/wake schedules and wake lag, potentially impairing health and educational outcomes.     

Sleep habits,circadian preferences and substance use in a Mexican population: the use of the Morningness-Eveningness-Stability-Scale improved (MESSi)

ABSTRACT

This study aimed to validate the Morningness-Eveningness-Stability-Scale improved (MESSi) in Mexico, analyzing the factor structure and sleep habits, combined with the proposal of cutoff values for the scales, and to assess the relationship with substance use. We applied the questionnaires through an online survey to a total sample of 510 Mexicans, aged 18–77 years (M = 27.79, SD = 10.24). The MESSi showed an acceptable fit and the Cronbach’s alpha coefficients were good to satisfactory in the Mexican sample in every subscale: Morning Affect (MA, α = 0.90), Eveningness (EV, α = 0.88), Distinctness (DI, α = 0.80). In order to obtain a better interpretation of the MESSi subscales, we decided to propose cutoff points corresponding to the 25th–75th percentile. The categories were depicted as strong trait presence, intermediate trait presence and weak trait presence. When applying the cutoff points for the MESSi sub-scales, with Morning Affect (MA), strong-types went to bed and woke up earlier and had more sleep than weak-types during weekdays and weekends and reported less social jetlag. For Eveningness (EV), strong-types went to bed and woke up later than weak-types on weekdays and weekends. Also, strong-types had a shorter time in bed during weekdays but not on weekends and reported more social jetlag. Lastly, with Distinctness (DI), the results reported that those with a strong-type showed greater amplitude on weekdays and weekends. Furthermore, the MESSi scale found that evening people consumed more alcohol and tobacco. Our study supported the validity and reliability of the MESSi in a Mexican population and the relationship between eveningness and substance consumption. Furthermore, the proposed cutoff scores for the MESSi sub-scales add a novel approach for the measurement and interpretation of the scale.     

Social jetlag,academic achievement and cognitive performance: Understanding gender/sex differences

Adolescents in high school suffer from circadian misalignment, undersleeping on weekdays and oversleeping on weekends. Since high schools usually impose early schedules, adolescents suffer from permanent social jetlag (SJL) and thus are a suitable population to study the effects of SJL on both academic and cognitive performance. In this study, 796 adolescents aged 12–16 years reported information about their sleep habits, morningness–eveningness (M–E), cognitive abilities and grade point average (GPA). Time in bed on both weekdays and weekends was not related to cognitive abilities, and only time in bed on weekdays was related to academic achievement. SJL was negatively related to academic achievement, cognitive abilities (except for vocabulary and verbal fluency abilities) and general cognitive ability (g), whereas M–E was slightly positively related to academic achievement and marginally negatively related to inductive reasoning. Results separated by sex/gender indicated that SJL may be more detrimental to girls’ performance, as it was negatively related to a greater number of cognitive abilities and GPA.     

Circadian rhythmicity of cortisol and body temperature: morningness-eveningness effects

The purpose of this study was to describe and compare the circadian rhythm of body temperature and cortisol, as well as self-reported clock times of sleep onset and offset on weekdays and weekends in 19 healthy adult "larks" (morning chronotypes) and "owls" (evening chronotypes), defined by the Home and Ostberg questionnaire. Day-active subjects entered the General Clinical Research Center, where blood was sampled every 2 h over 38 h for later analysis for cortisol concentration by enzyme immunoassay. Rectal body temperature was measured continuously. Lights were turned off at 22:30 for sleep and turned on at 06:00, when subjects were awakened. The acrophases (peak times) of the cortisol and temperature rhythms occurred 55 minutes (P < or = .05) and 68 minutes (P < .01), respectively, earlier in the morningness group. The amplitude of the cortisol rhythm was lower in the eveningness than in the morningness group (P = n.s.). Subject groups differed on all indices of habitual and preferred timing of sleep and work weekdays and weekends (P = .05-.001).     

Eveningness,Sleep Patterns,Daytime Functioning,and Quality of Life in Israeli Adolescents

The purpose of the study was to assess the relationships between eveningness, sleep patterns, measures of daytime functioning, i.e., sleepiness, sleep problem behaviors, and depressed mood, and quality of life (QOL) in young Israeli adolescents. A cross-sectional survey was performed in urban and rural middle schools in Northern Israel. Participants were 470 eighth and ninth grade middle school students (14?±?0.8 yrs of age) in the normative school system. Students completed the modified School Sleep Habits Survey (SSHS) and Pediatric Quality of Life Inventory Short Form, assessing six subscales of physical, emotional, social, school performance, and psychosocial functioning, plus an addition generated total score. During weekdays and weekends, evening types went to bed later, their sleep latency was longer, their wake-up time was later, and their sleep duration was shorter than intermediate and morning types. Evening types exhibited more sleep problem behaviors, sleepiness, depressed mood, and lower QOL compared to intermediate and morning types. Based on the regression model, sleepiness, sleep-problem behaviors, and depressed mood were the variables most strongly associated with QOL, followed by morning-evening preference, weekday sleep duration, and weekend sleep latency. This study is the first to assess QOL in normative, healthy adolescents and to demonstrate strong associations between morning-evening preference and QOL. These findings enhance the need to identify young individuals with an evening preference, and to be aware of the characteristics and manifestations of the evening chronotype on daytime and nighttime behaviors in adolescence. (Author correspondence: Orna@yvc.ac.il)     

Evening chronotype,late weekend sleep times and social jetlag as possible causes of sleep curtailment after maintaining perennial DST: ain’t they as black as they are painted?

ABSTRACT

People sleep less in response to setting social clocks earlier relative to the sun clocks. We proposed here a model-based approach for estimating sleep loss as the difference between weekend and weekday risetimes divided on the difference between weekend risetime and weekday bedtime. We compared this approach with a traditional approach to estimating sleep curtailment as the difference in weekly average sleep duration in two conditions. Weekday and weekend sleep times reported for 320 samples provided possibility of testing whether evening types with later weekend sleep times and larger social jetlag differ from morning types with earlier weekend sleep times and smaller social jetlag on amount of sleep lost (1) throughout the week and (2) in response to an advance of weekday wakeups, for instance, after the expected installation of perennial Daylight Saving Time (DST). We found that (1) an amount of sleep lost due to advancing shift of weekday wakeups depends upon neither chronotype nor weekend sleep times nor social jetlag, (2) a very large amount of sleep is usually lost by evening types with later weekend sleep times and larger social jetlag and (3) an essential sleep loss is caused by our usual work/school schedules, even in morning types with early weekend sleep times and small social jetlag. As compared to such permanent sleep losses experienced by any types, an additional loss due to switching from Standard Time (ST) to perennial DST are expected to be relatively small. We also found that the traditional way of calculation of sleep curtailment leads to paradoxical conclusions, such as (1) sleep loss is larger when social jetlag is smaller, not larger, (2) sleep loss is larger when weekend sleep times are earlier, not later, (3) despite 1-h difference between two student samples in weekday wakeups, their sleep losses can be identical.