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We surveyed the sleep‐wake patterns and lifestyle habits in a sample of Japanese first to third year junior high school children (n=638, age 12 to 15 yrs), of whom 29.3% were evening type, 64.1% intermediate type, and 6.6% morning type in preference. The morningness‐eveningness (M‐E) score was lower (more evening typed), 16.1 vs. 15.4 in first compared to third year students. There were significant gender differences, with girls showing a greater evening preference. Evening preference was associated with longer sleep latency, shortened sleep duration during schooldays and weekends, bad morning feeling, and episodes of daytime sleepiness. In contrast, morning preference was associated with higher sleep drive and better sleep‐wake parameters and lifestyle habits. Our results suggest the morning preference should be promoted among junior high school children to increase the likelihood of more regular sleep‐wake patterns and lifestyle habits.     

Chronotype and the transition to college life

Social synchronizers of morningness-eveningness, or chronotype, begin to change during the developmental transition from adolescence to college life. The current study examined how these changes related to the sleep/wake patterns of 220 undergraduates (93 males/122 females) ranging in age from 18 to 29 yrs at a private university. Coping strategies students used to deal with early morning commitments and familial conflict over sleep patterns were also examined. Results revealed that evening chronotypes were more likely to report conflict with parents in junior high school and high school over going to bed and waking, followed by a shift to a later sleep/wake pattern in college. They also reported adjusting their schedules and using more coping strategies to accommodate their evening bias. Morning chronotypes, whose routines easily fit a conventional morning schedule, reported little change in schedules and sleep patterns from junior high school to college, and used fewer coping strategies in response to early morning commitments. The shift in social zeitgebers from junior high school to college are significant, and yet little research has examined the effect these changes can have on students' adjustment to college life and the role that chronotype plays in this process. Because students' ability to cope with these changes will ultimately influence how successful they are in their various endeavors, a greater understanding of how chronotype is related to adaptive functioning across this developmental period is needed.     

The influence of chronotype in the daily lives of young children

Research on chronotypic differences has been conducted for many years, however, until recently, little attention has been paid to young children. The current study examined the influence of morningness–eveningness in the daily lives of 2 to 4 year olds (291 females, 230 males, 8 gender not given) via an online survey completed by 529 mothers from across the United States. The results replicated previous findings on chronotypic differences in sleep-wake patterns and the development of morningness–eveningness in early childhood. The influence of chronotype on sleep habits, daily routines and schedules was also explored. At both bed and wake times, mothers of evening type (E-type) children were more likely to report challenges. For a while, morning type (M-type) children tended to fall asleep easily and wake themselves up in the morning, E-types were more likely to show bedtime resistance, wake in a negative mood and have conflicts with their parents. In the morning, mothers of M-type children often stuck to their normal routine on days when the child had to be somewhere at 7:00 am, whereas mothers of E-type children employed different strategies to get their child up and out the door. Bedtime routines and daily schedules also differed by chronotype. Individual differences in morningness–eveningness and their impact on sleep-wake patterns and social interactions are evident early on. A greater understanding of how they affect the lives of young children and their future development is needed.     

Explaining sleep duration in adolescents: the impact of socio-demographic and lifestyle factors and working status

Previous studies found students who both work and attend school undergo a partial sleep deprivation that accumulates across the week. The aim of the present study was to obtain information using a questionnaire on a number of variables (e.g., socio-demographics, lifestyle, work timing, and sleep-wake habits) considered to impact on sleep duration of working (n = 51) and non-working (n = 41) high-school students aged 14-21 yrs old attending evening classes (19:00-22:30 h) at a public school in the city of S?o Paulo, Brazil. Data were collected for working days and days off. Multiple linear regression analyses were performed to assess the factors associated with sleep duration on weekdays and weekends. Work, sex, age, smoking, consumption of alcohol and caffeine, and physical activity were considered control variables. Significant predictors of sleep duration were: work ( p < 0.01), daily work duration (8-10 h/day; p < 0.01), sex ( p = 0.04), age 18-21 yrs (0.01), smoking( p = 0.02) and drinking habits ( p = 0.03), irregular physical exercise (p < 0.01), ease of falling asleep ( p = 0.04), and the sleep-wake cycle variables of napping ( p < 0.01), nocturnal awakenings ( p < 0.01), and mid-sleep regularity ( p < 0.01). The results confirm the hypotheses that young students who work and attend school showed a reduction in night-time sleep duration. Sleep deprivation across the week, particularly in students working 8-10 h/day, is manifested through a sleep rebound (i.e., extended sleep duration) on Saturdays. However, the different roles played by socio-demographic and lifestyle variables have proven to be factors that intervene with nocturnal sleep duration. The variables related to the sleep-wake cycle-naps and night awakenings-proved to be associated with a slight reduction in night-time sleep, while regularity in sleep and wake-up schedules was shown to be associated with more extended sleep duration, with a distinct expression along the week and the weekend. Having to attend school and work, coupled with other sociodemographic and lifestyle factors, creates an unfavorable scenario for satisfactory sleep duration.     

Chronotype and the Transition to College Life

Social synchronizers of morningness-eveningness, or chronotype, begin to change during the developmental transition from adolescence to college life. The current study examined how these changes related to the sleep/wake patterns of 220 undergraduates (93 males/122 females) ranging in age from 18 to 29 yrs at a private university. Coping strategies students used to deal with early morning commitments and familial conflict over sleep patterns were also examined. Results revealed that evening chronotypes were more likely to report conflict with parents in junior high school and high school over going to bed and waking, followed by a shift to a later sleep/wake pattern in college. They also reported adjusting their schedules and using more coping strategies to accommodate their evening bias. Morning chronotypes, whose routines easily fit a conventional morning schedule, reported little change in schedules and sleep patterns from junior high school to college, and used fewer coping strategies in response to early morning commitments. The shift in social zeitgebers from junior high school to college are significant, and yet little research has examined the effect these changes can have on students' adjustment to college life and the role that chronotype plays in this process. Because students' ability to cope with these changes will ultimately influence how successful they are in their various endeavors, a greater understanding of how chronotype is related to adaptive functioning across this developmental period is needed. (Author correspondence: lzimmerm@su.edu)     

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.     

Temperature profiles, and the effect of sleep on them, in relation to morningness-eveningness in healthy female subjects

There were 15 healthy female subjects, differing in their position on the “morningness-eveningness” scale, studied for 7 consecutive days, first while living a sedentary lifestyle and sleeping between midnight and 08:00 and then while undergoing a “constant routine.” Rectal temperature was measured at regular intervals throughout this time, and the results were subjected to cosinor analysis both before and after “purification” for the effects of physical activity. Results showed that there was a phase difference in the circadian rhythm of core temperature that was associated with the morningness score, with calculations that “morning types” would be phased earlier than “evening types” by up to about 3h. This difference in phase (which was also statistically significant when the group was divided by a median split into a “morning group” and an “evening group”) could not be attributed to effects of waking activity and existed in spite of the subjects keeping the same sleep-wake schedule. Moreover, it persisted when the subjects' data had been purified and when the data were obtained from the constant routine. That is, there was an endogenous component to this difference in phase of the core temperature. The morning group also showed a greater fall of core temperature during sleep; this was assessed in two ways, the main one being a comparison of constant routine and nychthemeral data sets after correction for any effects of activity. Even though the morning group was sleeping at a later phase of their circadian temperature rhythm than was the evening group, neither group showed a fall of temperature due to sleep that varied with time elapsed since the temperature acrophase. It is concluded that another factor that differs between morning and evening types is responsible for this difference. (Chronobiology International, 18(2), 227-247, 2001)     

The Relationships between Sleep-Wake Cycle and Academic Performance in Medical Students

Survey and laboratory studies suggest that several factors, such as social and academic demands, part-time jobs and irregular school schedules, affect the sleep-wake cycle of college students. In this study, we examined the sleep-wake pattern and the role played by academic schedules and individual characteristics on the sleep-wake cycle and academic performance. The subjects were 36 medical students (male = 21 and female = 15), mean age = 20.7 years, SD = 2.2. All students attended the same school schedule, from Monday to Friday. The volunteers answered a morningness-eveningness questionnaire, the Pittsburgh Sleep Quality Index (PSQI) and kept a sleep-wake diary for two weeks. The relationships between sleep-wake cycle, PSQI, chronotypes and academic performance were analyzed by a multiple regression technique. The results showed that 38.9% of the students had a poor sleep quality according to the PSQI. When the medical students were evening type or moderate evening type the PSQI showed a tendency of poor sleep. The multiple regression analysis showed a correlation between sleep onset, sleep irregularity and sleep length with academic performance. These results suggest that chronotypes influence the quality of the sleep-wake cycle and that irregularity of the sleep-wake cycle, as well as sleep deprivation (average length was 6:52), influence the learning of college students.     

The Relationships between Sleep-Wake Cycle and Academic Performance in Medical Students

Survey and laboratory studies suggest that several factors, such as social and academic demands, part-time jobs and irregular school schedules, affect the sleep-wake cycle of college students. In this study, we examined the sleep-wake pattern and the role played by academic schedules and individual characteristics on the sleep-wake cycle and academic performance. The subjects were 36 medical students (male = 21 and female = 15), mean age = 20.7 years, SD = 2.2. All students attended the same school schedule, from Monday to Friday. The volunteers answered a morningness-eveningness questionnaire, the Pittsburgh Sleep Quality Index (PSQI) and kept a sleep-wake diary for two weeks. The relationships between sleep-wake cycle, PSQI, chronotypes and academic performance were analyzed by a multiple regression technique. The results showed that 38.9% of the students had a poor sleep quality according to the PSQI. When the medical students were evening type or moderate evening type the PSQI showed a tendency of poor sleep. The multiple regression analysis showed a correlation between sleep onset, sleep irregularity and sleep length with academic performance. These results suggest that chronotypes influence the quality of the sleep-wake cycle and that irregularity of the sleep-wake cycle, as well as sleep deprivation (average length was 6:52), influence the learning of college students.     

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)     

Subjective sleep quality exclusively mediates the relationship between morningness-eveningness preference and self-perceived stress response

Eveningness preference has been associated with lower sleep quality and higher stress response compared with morningness preference. In the current study, female morning (n = 27) and evening (n = 28) types completed the Pittsburgh Sleep Quality Index (PSQI) and were additionally challenged with an arithmetic stress-induction task. Evening types reported lower subjective sleep quality and longer sleep latency than morning types. Furthermore, evening types reported higher self-perceived stress after the task than morning types. Subjective sleep quality fully mediated the relationship between morningness-eveningness preference and stress response. Poor sleep quality may, therefore, contribute to the elevated health risk in evening types.     

Evening preference is related to the incidence of depressive states independent of sleep-wake conditions

Although evening preference has recently been identified as a risk factor for depression, it has not been substantiated whether evening preference is a direct risk factor for depressive states, or if it is associated secondarily through other factors, such as delayed sleep timing and shortened sleep duration. The objective of this study is to investigate associations in Japanese adult subjects between evening preference and incidence of depressive states, adjusting for various sleep parameters related to depressive states. The Morningness-Eveningness Questionnaire (MEQ), the Pittsburgh Sleep Quality Index (PSQI), and the Center for Epidemiologic Studies Depression Scale (CES-D) were administered to 1170 individuals (493 males/677 females; mean and range 38.5 and 20-59 yrs) to assess their diurnal preferences, sleeping states, and presence of depression symptoms. Subjects were classified into five chronotypes based on MEQ scores. Evening preference was associated with delayed sleep timing, shortened sleep duration, deteriorated subjective sleep quality, and worsened daytime sleepiness. Logistic regression analysis demonstrated that the extreme evening type (odds ratio [OR]?=?1.926, p?=?.018) was associated with increased incidence of depressive states and that the extreme morning type (OR?=?0.342, p?=?.038) was associated with the decreased incidence of depressive states, independent of sleep parameters, such as nocturnal awakening (OR?=?1.844, p?相似文献   

The Influence of Study Schedules and Work on the Sleep–Wake Cycle of College Students

College students usually exhibit an irregular sleep-wake cycle characterized by great phase delays on weekends and short sleep length on weekdays. As the temporal organization of social activities is an important synchronizer of human biological rhythms, we investigated the role played by study's schedules and work on the sleep-wake cycle. Three groups of female college students were investigated: (1) no-job morning group, (2) no-job evening group, (3) job evening group. The volunteers answered a sleep questionnaire in the classroom. The effects of day of the week and group on the sleep schedules and sleep length were analyzed by a two way ANOVA for repeated measures. The three groups showed delays in the wake up time on weekends. No-job evening and morning groups also delayed bedtime, but the job evening group slept at the same time on weekdays as on weekends. Sleep length increased on weekends for morning group and job evening group, whereas the no-job evening group maintained the amount of sleep from weekdays to weekends. This survey showed that the tendency of phase delay on weekends was differently expressed according to study's schedules and work.     

The Influence of Study Schedules and Work on the Sleep-Wake Cycle of College Students

College students usually exhibit an irregular sleep-wake cycle characterized by great phase delays on weekends and short sleep length on weekdays. As the temporal organization of social activities is an important synchronizer of human biological rhythms, we investigated the role played by study's schedules and work on the sleep-wake cycle. Three groups of female college students were investigated: (1) no-job morning group, (2) no-job evening group, (3) job evening group. The volunteers answered a sleep questionnaire in the classroom. The effects of day of the week and group on the sleep schedules and sleep length were analyzed by a two way ANOVA for repeated measures. The three groups showed delays in the wake up time on weekends. No-job evening and morning groups also delayed bedtime, but the job evening group slept at the same time on weekdays as on weekends. Sleep length increased on weekends for morning group and job evening group, whereas the no-job evening group maintained the amount of sleep from weekdays to weekends. This survey showed that the tendency of phase delay on weekends was differently expressed according to study's schedules and work.     

Ethnic differences in sleep duration and morning–evening type in a population sample

This cross-sectional population study examined associations of sleep duration and morning–evening type with sociodemographic and cardiometabolic disease in adults participating in the UK Biobank study (N = 439 933). Multivariable Poisson regression models of sleep duration and morning–evening type with a robust error variance were generated to estimate adjusted prevalence ratios and their 95% confidence intervals. All models were adjusted for sex, race, college attendance, employment status and age. Twenty five percent of the sample reported short sleep; 27% were morning, 64% intermediate and 9% evening type. Black ethnicity emerged as most strongly associated with sleep behavior. Short sleep was twice as prevalent, and morning versus intermediate type was 1.4 times more prevalent in Black than White participants. The greater prevalence of short sleep and morning type among Blacks suggests that sleep-based approaches to improving cardiometabolic outcomes may require a more multidimensional approach that encompasses adequate sleep and circadian alignment in this population.     

Parents’ assessment of circadian preference in elementary school-aged children: Validity and relations to educational outcomes

Meta-analyses suggest that morning-oriented students obtain better school grades than evening-oriented students. This finding has generally been found for students in high school using self-report data for the assessment of circadian preference. Two studies (N = 2718/192) investigated whether these findings generalize across samples (i.e. elementary school-aged students) and methods (i.e. parent reports). These studies also explored whether the relation between circadian preference and school achievement could be explained within an expectancy-value framework. To this end, the Lark-Owl Chronotype Indicator (LOCI) was modified to obtain parents’ evaluations of their children’s circadian preference, while students completed a battery of assessments designed to explore the test-criterion evidence. Structural equation modeling and correlational analyses revealed: (1) morning and evening orientation were two separable factors of children’s circadian preference; (2) correlations with behavioral (e.g. sleep and eating times) and psychological (e.g. cognitive ability) data supported the test-criterion validity of both factors; (3) morning orientation was positively related to school achievement and (4) consistent with an expectancy-value framework this relation was mediated by children’s academic self-concept (ASC). These findings have important research and policy implications for considering circadian preference in the schooling of elementary students.     

Validation of Horne and Ostberg morningness-eveningness questionnaire in a middle-aged population of French workers

As suggested by the authors, the Horne and Ostberg morning/evening questionnaire (MEQ) has never been adapted to evaluate a nonstudent population. The purpose of this study was to validate this MEQ in a sample of middle-aged workers by modifying only the cutoffs. It was administered in 566 non-shift-workers aged 51.2 to 3.2 years who presented no sleep disorders. According to the Home and Ostberg classification, the sample consisted of 62.1% morning type, 36.6% neither type, and 2.2% evening type. Multiple correspondence analysis, which determines the principal components, was performed on all MEQ items. Then an ascending hierarchical classification was applied to determine 3 clusters from these principal components. On the basis of these 3 clusters, new cutoffs were determined: evening types were considered as scoring under 53 and morning types above 64, thus giving 28.1% morning type, 51.7% neither type, and 20.2% evening type. As an external validation, eveningness was associated with later bedtime and waking-up time (more pronounced at the weekend), greater need for sleep, larger daily sleep debt, greater morning sleepiness, and ease of returning to sleep in the early morning. A positive correlation between age and morningness was again found. This study confirms that "owls" are not rare in a middle-aged sample. We conclude that this adapted MEQ could be useful when investigating age-related changes in sleep.     

Association Between Moringness‐Eveningness Preference and Mental/Physical Premenstrual Symptoms in Japanese Females 12 to 31 Years of Age

This study investigates the relationship between circadian typology, i.e., morningness‐eveningness (M‐E) preference, and the occurrence and severity of premenstrual mental and physical symptoms among 154 young Japanese female university students (range, 18 to 31 yrs; mean±S.D., 20.69±3.69 yrs) and 417 junior high school students (range, 12 to 15 yrs; mean±S.D., 14.29±0.67 yrs) living in an urban or suburban area of Kochi prefecture. Female university students experienced melancholy mood more frequently than did males, and the female university students who frequently became melancholy were more evening‐typed than those who did not experience melancholy. Female university students who experienced frequent fluctuations in mood and/or menstrual pain were more evening‐typed than those who were not so affected. M‐E preference of junior high school students was not correlated with stability of mood or frequency of menstrual pain. In urban areas, however junior high school students who had very stable menstrual cycles were significantly more morning‐typed than those whose menstrual cycles were not stable. In suburban areas, the bedtimes of female junior high students who had stable menstrual cycles were significantly earlier than those whose menstrual cycle duration was not stable. A physiological relationship between the circadian system, M‐E, and attributes of the menstrual cycle seems to be present in adolescent female Japanese junior high school students.     

The self-morningness/eveningness (Self-ME): An extremely concise and totally subjective assessment of diurnal preference

The assessment of diurnal preference, or the preferred timing of sleep and activity, is generally based on comprehensive questionnaires such as the Horne–Östberg (HÖ). The aim of the present study was to assess the reliability of a subject’s self-classification as extremely morning (Self-MM), more morning than evening (Self-M), more evening than morning (Self-E) or extremely evening (Self-EE) type, based on the last question of the HÖ (Self-ME). A convenience sample of 461 subjects [23.8?±?4.7 years; 322 females] completed a full sleep–wake assessment, including diurnal preference (HÖ), night sleep quality (Pittsburgh Sleep Quality Index, PSQI), daytime sleepiness (Karolinska Sleepiness Scale, KSS), and habitual sleep–wake timing (12?d sleep diaries; n?=?296). Significant differences in HÖ total score were observed between Self-ME classes, with each class being significantly different from neighboring classes (p?<?0.0001). Significant differences in sleep–wake timing (bed time, try to sleep and sleep onset, wake up, and get up time) were observed between Self-ME classes. Such differences were maintained when sleep–wake habits were analysed separately on work and free days, and also in a smaller group of 67 subjects who completed the Self-ME as a stand-alone rather than as part of the original questionnaire. Significant differences were observed in the time-course of subjective sleepiness by Self-ME class in both the large and the small group, with Self-MM and Self-M subjects being significantly more alert in the morning and sleepier in the evening hours compared with their Self-E and Self-EE counterparts. Finally, significant differences were observed in night sleep quality between Self-ME classes, with Self-EE/Self-E subjects sleeping worse than their Self-MM/Self-M counterparts, and averaging just over the abnormality PSQI threshold of 5. In conclusion, young, healthy adults can define their diurnal preference based on a single question (Self-ME) in a way that reflects their sleep–wake timing, their sleepiness levels over the daytime hours, and their night sleep quality. Validation of the Self-ME across the decades and in diseased populations seems worthy.     

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.