A Study of the Association between Sleep Habits and Problematic Behaviors in Preschool Children

This preliminary study examined the association between sleep habits and problematic behaviors in healthy preschool children using an internationally standardized method. Two groups of 4–6‐yr‐old healthy Japanese children were recruited. Children in Group A (n=68) met one or more of the following three conditions: they went out from their home with adults after 21∶00 h two or more times a week, they went to bed after 23∶00 h four or more times a week, and they returned home after 21∶00 h three or more times a week, while those in Group B (n=67) met none of these conditions. Sleep‐wake logs and the Child Behavior Checklist (CBCL)/4–18 were completed daily for two weeks. The CBCL consists of questions with 113 items categorized into eight subscale items: (I) Withdrawn, (II) Somatic complaints, (III) Anxious/depressed, (IV) Social problems, (V) Thought problems, (VI) Attention problems, (VII) Delinquent behavior, and (VIII) Aggressive behavior. Internalizing (I+II+III), externalizing (VII+VIII), and total scale scores were also derived. Generally, the higher the score, the greater the likelihood of problematic behaviors in that scale. We compared both the CBCL scores and distribution of the CBCL score‐determined clinical classification of behavior (normal, borderline, and abnormal) between the groups. Correlation coefficients between CBCL scores and each of the seven indices of the studied sleep habits (wake‐up times, bedtimes, nocturnal sleep duration, nap duration, total sleep duration, and range of variation in wake‐up and bedtime) were also assessed. Group A children showed significantly shorter average nocturnal sleep, nap, and total sleep duration, significantly later average bedtimes and wake‐up times, and a significantly greater range of variation in bedtimes and wake‐up times than Group B children. The CBCL score of the total scale was significantly higher in Group A than Group B children. The distribution of the clinical classifications of behavior between the two groups showed no significant differences. Although nocturnal sleep, nap, and total sleep duration did not correlate with total CBCL score, it showed a high positive correlation with wake‐up times, bedtimes, and ranges of variation in both wake‐up and bed times. The distribution of the clinical classification for the total scale showed significant differences between early and late risers, and also between regular and irregular sleepers. The number of children classified as normal for the total scale score was higher in early risers and regular sleepers than in late risers and irregular sleepers. Preschool children of Group A, late risers, late sleepers, irregular risers, and irregular sleepers were likely to show problematic behaviors.     

Sleep patterns and sleep problems among Egyptian school children living in urban,suburban, and rural areas

The present study was conducted to determine the prevalence of sleep patterns and sleep problems among Egyptian school-aged children and to compare sleep patterns and sleep problems among school children from urban, suburban, and rural areas. In this cross-sectional survey, parents of 629 school-aged children, aged 6 to 10 years, from 15 elementary schools in five rural, urban, and suburban areas in the Giza governorate, Egypt, completed the Arabic version of the Children’s Sleep Habits Questionnaire (CSHQ) and questions about parents’ level of education and significant medical problems and/or medication for the child. The mean (SD) of total sleep duration for all children was 8.96 h (SD, 1.20). The most prevalent CSHQ subscales were: bedtime resistance, daytime sleepiness, and night wakings. There were significant differences regarding bedtime (P= 0.006) and night-time sleep duration (P < 0.001) among school children from different areas, but there were no significant differences regarding wake-up time, total sleep duration, duration of nap, and the eight CSHQ subscale scores. The percentage of children who took a daytime nap was 52.9% (n= 184) and the mean (SD) duration of a nap was 1.5 h (SD, 0.92). Paternal illiteracy was associated with higher CSHQ total score and many subscales. In conclusion, sleep duration was shorter than that reported in previous studies. Sleep problems are fairly common among elementary school children in the Giza governorate, whether in urban, suburban, or rural areas. Paternal level of education has an impact on the prevalence of sleep problems.

     

Dynamical properties of the two-process model for sleep-wake cycles in infantile autism

The two-process model is a scheme for the timing of sleep that consists of homeostatic (Process S) and circadian (Process C) variables. The two-process model exhibits abnormal sleep patterns such as internal desynchronization or sleep fragmentation. Early infants with autism often experience sleep difficulties. Large day-by-day changes are found in the sleep onset and waking times in autistic children. Frequent night waking is a prominent property of their sleep. Further, the sleep duration of autistic children is often fragmented. These sleep patterns in infants with autism are not fully understood yet. In the present study, the sleep patterns in autistic children were reproduced by a modified two-process model using nonlinear analysis. A nap term was introduced into the original two-process model to reproduce the sleep patterns in early infants. The nap term and the time course of Process S are mentioned in the present study. Those parameters led to bifurcation of the sleep-wake cycle in the modified two-process model. In a certain range of these parameter sets, a small external noise was amplified, and an irregular sleep-wake cycle appeared. The short duration of sleep led to another irregular sleep onset or waking. Consequently, an irregular sleep-wake cycle appeared in early infantile autism.     

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.     

Epidemiological study on chronotype among preschool children in Japan: Prevalence,sleep–wake patterns,and associated factors

Our current 24-h society and the weekday–weekend switch of our social clocks may affect young children’s sleep and circadian rhythms. However, such evidence is scarce. We conducted a nationwide epidemiological study of sleep and health in preschool children aged 3–5 years attending kindergarten or childcare centers in Japan, using stratified one-stage cluster sampling. The target population was 2 969 627 individuals (as of 1 April 2013). The Children’s ChronoType Questionnaire was used to measure chronotypes (morning (M)-type, neither (N)-type and evening (E)-type), and weekday and weekend sleep–wake parameters. Randomly sampled population estimates were obtained via respondents with a person-level weight, which accounted for survey responses and poststratification. Standard errors and 95% confidence intervals were adjusted for the complex survey design using jackknife estimation. A linear regression model of the correlation between chronotype and sleep–wake parameters and a multivariate logistic regression model for the links between chronotype and putative associated factors were used for statistical analyses. The estimated prevalence of M-, N- and E-types were 31.6%, 55.9% and 10.0%, respectively. The corresponding numbers of children were 937 910, 1 659 574 and 296 083. The remaining 2.5% was not specified. The proportions of children who woke up by themselves during the weekdays were 55.1%, 43.0% and 1.9% for M-, N- and E-types, respectively. Overall, bedtime, sleep onset time, wake-up time and get-up time during the weekdays were 21:04, 21:26, 6:55 and 6:59, respectively. Nocturnal sleep period, time in bed (TIB) and 24 h TIB (TIB and nap) during the weekdays were 9.49, 9.93 and 10.55 h, respectively. Sleep–wake timings were significantly and linearly delayed from M-, N-, to E-types (p < 0.001). The weekday 24 h TIB (10.47–10.66 h) and weekend nocturnal sleep period (9.58–9.76 h) did not differ significantly among chronotypes. For E-types, socially advanced weekdays rising times (approximately 1 h) caused nocturnal sleep deficit (0.57 h). Children’s socially scheduled times (e.g. start and finish times, mealtimes and daytime nap) and their parents’ diurnal preferences had significant adjusted odds ratios among E-types, while the significant unadjusted odds ratios for morning sunlight and multimedia exposure disappeared. These results suggest the importance of chronobiologically planned sleep discipline at home as well as assessment of socially scheduled times in children.     

Are parents’ working patterns associated with their child’s sleep? An analysis of dualparent families in Australia

Insufficient sleep in children predicts emotional and behavioral problems, poorer school performance, and health problems. Child sleep durations have declined in recent decades, suggesting a need to identify and understand predictors of short sleep. The present study investigated whether aspects of parental employment (i.e. parental work hours, and non-standard work hours) were associated with sleep in children. Data collected from 2477 children aged 6-7 years as part of the Longitudinal Study of Australian Children were used in this paper. Child sleep duration, bedtimes, and wake times were determined from parent self-report using time-use diaries. Parents completed a survey assessing their work patterns as well as a range of other demographic and social factors. The results indicated that long mother work hours were associated with later bedtimes and increased odds of <9.5 h sleep in children. Long father work hours were associated with earlier waketimes, earlier bedtimes, and reduced odds of long sleep. Non-standard work hours were associated with longer sleep and earlier bedtimes. The present results indicate the need to develop strategies to limit any adverse effects of parental work on child sleep, perhaps by promoting earlier and regular bedtimes. These findings warrant further investigation given the importance of sleep in healthy child development.

     

Social jetlag affects subjective daytime sleepiness in school-aged children and adolescents: A study using the Japanese version of the Pediatric Daytime Sleepiness Scale (PDSS-J)

The aim of this study was to elucidate the level of daytime sleepiness in Japanese school-aged children and adolescents, and to examine associated factors including sleep loss and social jetlag using the Japanese version of the Pediatric Daytime Sleepiness Scale (PDSS-J). After the linguistic validation of the PDSS-J with a multi-step translation methodology, consisting of forward translation, back translation, expert review and cognitive debriefing interviews, we conducted a psychometric validation for 492 students aged 11–16 years (46.7% boys) of public elementary school, junior high school and high school, using the PDSS-J, the Karolinska Sleepiness Scale (KSS), and bedtimes and wake-up times on school days and free days. Internal consistency (Cronbach’s alpha) of the PDSS-J was 0.77, and the test–retest reliability demonstrated by the intraclass coefficient was 0.88. Multivariate logistic regression analysis revealed that both short sleep duration and social jetlag were identified as factors associated with daytime sleepiness, after adjustment for age and sex. PDSS-J scores were significantly higher in the group with large social jetlag with or without sufficient sleep duration than in the group with sufficient sleep duration and small social jetlag. The PDSS-J is an important tool for assessing daytime sleepiness, given its ease of administration and robust psychometric properties. The impact of not only sleep loss but also social jetlag on daytime sleepiness among school-aged children and adolescents must be fully taken into account.     

小醒脑针刺法联合度洛西汀对持续性姿势-知觉性头晕患者心理状态、平衡功能及睡眠质量的影响

摘要 目的：探讨小醒脑针刺法联合度洛西汀对持续性姿势-知觉性头晕（PPPD）患者心理状态、睡眠质量及平衡功能的影响。方法：收集2017年1月~2019年6月期间我院收治的70例PPPD患者为研究对象。按门诊号单双数将研究对象分为对照组（n=35,度洛西汀治疗）和研究组（n=35,小醒脑针刺法联合度洛西汀治疗）,对比两组头晕发作频次、头晕发作持续时间以及眩晕残障程度评定量表（DHI）评分、汉密尔顿抑郁量表（HAMD）评分、汉密尔顿焦虑量表（HAMA）评分、Berg平衡量表（BBS）评分、活动平衡信心量表（ABC）评分、微觉醒指数、入睡后清醒时间、睡眠分期转换次数、醒转次数、匹兹堡睡眠质量指数（PSQI）评分。结果：两组治疗后头晕发作频次、头晕发作持续时间、微觉醒指数、入睡后清醒时间、睡眠分期转换次数、醒转次数以及DHI、PSQI、HAMA、HAMD评分均较治疗前降低,且研究组较对照组低（P<0.05）。治疗后两组BBS、ABC评分均较治疗前升高,且研究组较对照组高（P<0.05）。结论：小醒脑针刺法联合度洛西汀治疗PPPD患者,可有效改善患者眩晕症状、心理状态、睡眠质量及平衡功能。     

Sleep habits of Iranian pre-school children in an urban area: Late sleeping and sleep debt in children

Using BEARS (Bedtime problems, Excessive sleepiness, Awakenings during the night, Regularity of sleep, Snoring), and CSHQ (Children’s Sleep Habits Questionnaires) screening tools with 224 participants revealed that Iranian children have shorter night sleep duration than expected (9.54 vs 12 h) for their age group. Earlier sleepers had longer night sleep duration (10:36 ± 1:12; 9:12 ± 1:06 h, P > 0.001), and total daily sleep time (11:36 ± 1:42; 10:36 ± 1:30 h, P = 0.005) than late sleepers. A majority (85%) of naptakers had sleep bedtime of 22:00 or later. The poor sleep quality of Iranian preschool children is probably due to cultural characteristics, climate differences, or harmful sleep habits.

     

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.     

Role of sleep timing in caloric intake and BMI

Sleep duration has been linked to obesity and there is also an emerging literature in animals demonstrating a relationship between the timing of feeding and weight regulation. However, there is a paucity of research evaluating timing of sleep and feeding on weight regulation in humans. The goal of this study was to evaluate the role of sleep timing in dietary patterns and BMI. Participants included 52 (25 females) volunteers who completed 7 days of wrist actigraphy and food logs. Fifty-six percent were "normal sleepers" (midpoint of <5:30 AM) and 44% were "late sleepers" (midpoint of sleep ≥5:30 AM). Late sleepers had shorter sleep duration, later sleep onset and sleep offset and meal times. Late sleepers consumed more calories at dinner and after 8:00 PM, had higher fast food, full-calorie soda and lower fruit and vegetable consumption. Higher BMI was associated with shorter sleep duration, later sleep timing, caloric consumption after 8:00 PM, and fast food meals. In multivariate models, sleep timing was independently associated with calories consumed after 8:00 PM and fruit and vegetable consumption but did not predict BMI after controlling for sleep duration. Calories consumed after 8:00 PM predicted BMI after controlling for sleep timing and duration. These findings indicate that caloric intake after 8:00 PM may increase the risk of obesity, independent of sleep timing and duration. Future studies should investigate the biological and social mechanisms linking timing of sleep and feeding in order to develop novel time-based interventions for weight management.     

Short sleep and late bedtimes are detrimental to educational learning and knowledge transfer: An investigation of individual differences in susceptibility

Good sleep hygiene practices, including consistent bedtimes and 7–9 h of sleep/night, are theorized to benefit educational learning. However, individuals differ in how much sleep they need, as well as in their chronotype preference. Therefore, some students may be more vulnerable to the cognitive effects of sleep loss, later bedtimes and nonpreferred times of learning than others. One prominent example is the debate regarding whether sleep loss and later bedtimes affect classroom learning more in female or male students. To inform this gender-and-sleep-loss debate, we developed a virtual college-level lecture to use in a controlled, laboratory setting. During Session 1, 78 undergraduate students were randomly assigned to take the lecture at 12:00 (noon condition) or 19:30 (evening condition). Then participants wore wristband actigraphy for 1 week to monitor average and intraindividual variability in sleep duration, bedtime and midpoint of sleep. During Session 2, participants completed a test at the same time of day as Session 1. The test included basic questions that were similar to trained concepts during the lecture (trained items) as well as integration questions that required application of learned concepts (knowledge-transfer items). Bayesian analyses supported the null hypothesis that time of learning did not affect test performance. Collapsed across time of testing, regression analyses showed that shorter sleep durations and later bedtimes explained 13% of the variance in test performance. Longer sleep durations and earlier bedtimes predicted better test performance primarily in females, younger students and morning-types. Interestingly, students with above-median fluid intelligence scores were resilient to short sleep and late bedtimes. Our findings indicate that both sleep and circadian factors should be addressed to optimize educational learning, particularly in the students who are most susceptible to sleep loss.     

Neuropsychological Outcomes of Nocturnal Asthma

In spite of frequent reports that nocturnal asthma results in fatigue and impaired cognitive performance, there exists little objective evidence as to the daytime consequences of this disorder. Treatment studies have established that the symptoms of nocturnal asthma improve with medication intervention, but performance does not. Studies of obstructive sleep apnea (OSA), a source of generally more severe sleep fragmentation, have demonstrated that measurement of sleep-deprivation effects is limited to tasks requiring heightened alertness and rapid information processing, and that the degree of score change is related to the degree of sleep disruption. Studies of normal, but sleep-deprived, subjects indicate that (1) utilization of repetitive measures sustained for long duration can potentiate motivation to overcome the effects of fatigue in the laboratory, and (2) even when average scores do not change significantly, performance becomes more irregular. These collective findings about the measurement of performance impairment secondary to sleep deprivation can be used to guide new studies of nocturnal asthma. Finally, children must be included in future investigations because they may be at even greater risk for daytime consequences of nocturnal asthma than adults.     

Neuropsychological Outcomes of Nocturnal Asthma

In spite of frequent reports that nocturnal asthma results in fatigue and impaired cognitive performance, there exists little objective evidence as to the daytime consequences of this disorder. Treatment studies have established that the symptoms of nocturnal asthma improve with medication intervention, but performance does not. Studies of obstructive sleep apnea (OSA), a source of generally more severe sleep fragmentation, have demonstrated that measurement of sleep-deprivation effects is limited to tasks requiring heightened alertness and rapid information processing, and that the degree of score change is related to the degree of sleep disruption. Studies of normal, but sleep-deprived, subjects indicate that (1) utilization of repetitive measures sustained for long duration can potentiate motivation to overcome the effects of fatigue in the laboratory, and (2) even when average scores do not change significantly, performance becomes more irregular. These collective findings about the measurement of performance impairment secondary to sleep deprivation can be used to guide new studies of nocturnal asthma. Finally, children must be included in future investigations because they may be at even greater risk for daytime consequences of nocturnal asthma than adults.     

Sleep/wake patterns and circadian typology in preschool children based on standardized parental self-reports

We studied the sleep/wake patterns and circadian typology of Japanese preschool children living in the Tokyo metropolitan area (193 boys and 190 girls, 4–6 years of age) from June to July 2012 based on a standardized parental self-reporting questionnaire. Our major findings are as follows: (1) sleep/wake timing was delayed, and the duration of nocturnal sleep (sleep period as well as time in bed) increased from that on scheduled days (weekdays) to that on free days (weekends) for all ages. (2) The duration of daily sleep (24?h), including daytime nap, was longer for 4-year-old children compared with that in 5- to 6-year-old children, but not significantly different between scheduled and free days within each age group. (3) The distribution of chronotypes was 36.3% for morning (M)-type, 48.8% for neither (N)-type and 11.2% for evening (E)-type, and this distribution was independent of sex or age. (4) Sleep/wake timing delays were observed from M-type and N-type to E-type during scheduled and free days. (5) The duration of nocturnal sleep decreased but increased for 24-h sleep time from M-type and N-type to E-type on scheduled days. (6) Sleep durations did not differ among chronotypes on free days. (7) Chronotypes were associated with parents’ diurnal preferences, mealtimes and attendance at kindergartens or childcare centers but not with sex, age, season of birth, exposure to multimedia or exposure to morning sunlight in their bedrooms. When these results were compared with those for older children and adolescents, similar sleep/wake patterns and circadian typology were observed, although to a lesser degree, in children as young as 4–6 years of age. Napping may compensate, in part, for an accumulated weekday sleep deficit. The distribution of chronotypes was associated with differences in sleep/wake timing and duration and was influenced by the parents’ diurnal preferences and lifestyles. Further research on preschool children is required to investigate whether circadian typology affects their behavioral, emotional and cognitive development.     

Circadian phase estimation of chronic insomniacs relates to their sleep characteristics

The significance of the phase of circadian rhythmicity for the diagnosis of sleep disturbance was investigated in a group of 80 chronic insomniacs (59 females; mean age 34.8, range 18-59 years). In order to stay close to common clinical practice, data were collected by means of two-week sleep diaries in combination with repeated measurements of subjective alertness and oral temperature. Special measures were taken to minimize the impact of masking upon the temperature measurements. In addition, wrist activity was monitored for an overlapping period of 11 days. Measurements of oral temperature and subjective alertness were fitted with 3 (rd) -degree polynomials, for which the peak times (times of maximum) were identified. Principal Components Analysis of these peak times and the times of bed-in and wake-up for all subjects revealed that the phase estimates for the alertness and the sleep-wake rhythms had a strong interrelationship, which was independent from the temperature phase. Using the 25- and the 75-percentiles of the frequency distribution of the temperature peak times as boundaries, the subjects were classified into early (N = 18), middle (N = 37) and late (N = 19) temperature phase subgroups, which had mean peak times of 14:08 h, 17:43 h and 20:09 h, respectively. Comparisons between the early phase and the late phase subgroups showed that a significant overall MANOVA effect was mainly due to differences in total sleep time (early < late) as calculated from the log, and to differences in the mean nocturnal actigraphic count (early> late). Moreover, the subjective estimates of sleep latency (early < late) and wake after sleep onset (early > late) tended to differ between the two subgroups. The main result of this study, i.e., that insomniacs with a relatively advanced temperature phase had a relatively shorter and more restless sleep, while insomniacs with a relatively delayed temperature phase tended to experience a relatively long sleep latency, supports the conclusion that the addition of oral temperature measurements to a sleep/wake log extends its diagnostic and therapeutic applicability.     

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.     

Delayed sleep/wake rhythm and excessive daytime sleepiness correlate with decreased daytime brain activity during cognitive task in university students

Insufficient sleep and irregular sleep/wake rhythm are common problems among university students. We investigated the effect of sleep/wake rhythm and excessive daytime sleepiness (EDS) on the cortical oxygenation as measured by near-infrared spectroscopy (NIRS) and cognitive performance in university students. Peak- and integral values by a word fluency task were measured with NIRS. EDS was evaluated by the Epworth sleepiness scale (ESS), and performance function was evaluated using N-back task. Peak cerebral oxygenation was significantly correlated with ESS, bedtime, wake-up time, and median time of sleep. Accuracy on 2-back task was significantly correlated with integral value. Peak- and integral values were significantly lower, and bedtime and median time of sleep were significantly delayed in the EDS group than in the non-EDS group. EDS accompanied by delayed sleep/wake rhythm and short sleep duration may play an important role in decreasing daytime brain activity and cognitive performance.