Age- and height-dependent bias of underweight and overweight assessment standards for children and adolescents.

Background: Precision in evaluating underweight and overweight status among children and adolescents is paramount for averting health and developmental issues. Existing standards for these assessments have faced scrutiny regarding their validity. This study investigates the age and height dependencies within the international standards set by the International Obesity Task Force (IOTF), relying on body mass index (BMI), and contrasts them with Japanese standards utilizing the percentage of overweight (POW). Method: We scrutinized a comprehensive database comprising 7,863,520 children aged 5-17 years, sourced from the School Health Statistics Research initiative conducted by Japan's Ministry of Education, Culture, Sports, Science, and Technology. Employing the quantile regression method, we dissected the structure of weight-for-height distributions across different ages and sexes, quantifying the potentially biased assessments of underweight and overweight status by conventional criteria. Results: Applying IOFT criteria for underweight assessment revealed pronounced height dependence in males aged 11-13 and females aged 10-11. Notably, a discernible bias emerged, wherein children in the lower 25th percentile were classified as underweight five times more frequently than those in the upper 25th percentile. Similarly, the overweight assessment displayed robust height dependence in males aged 8-11 and females aged 7-10, with children in the lower 25th percentile for height deemed obese four or five times more frequently than their counterparts in the upper 25th percentile. Furthermore, using the Japanese POW criteria for assessment revealed significant age dependence in addition to considerably underestimating the percentage of underweight and overweight cases under the age of seven. However, the height dependence for the POW criterion was smaller than the BMI criterion, and the difference between height classes was less than 3-fold. Conclusion: Our findings underscore the intricacies of age-dependent changes in body composition during the growth process in children, emphasizing the absence of gold standards for assessing underweight and overweight. Careful judgment is crucial in cases of short or tall stature at the same age, surpassing sole reliance on conventional criteria results.

Sleep characteristics in underweight young females across their menstrual cycles: A sleep-monitoring survey study with preliminary results.

This study investigated the association between underweight and sleep in young females across their menstrual cycles. A lifestyle-monitoring survey was conducted among 38 female university students aged 18-24 years in Japan from January to December 2023. Sleep data from 28 participants were analysed. Participants were categorized into underweight (n = 10) and control (n = 18) groups based on a baseline body mass index cut-off of 18.5 kg m-2. Sleep parameters were assessed using a daily sleep questionnaire, sleep sensor mats, and urinary melatonin metabolites across their menstrual cycles. The results indicated no significant differences in sleep patterns between the underweight and control groups or menstrual cycle phases, as assessed using both the daily sleep questionnaire and the sleep sensor mats. However, underweight participants experienced more difficulty maintaining sleep during the follicular phase. Body mass index significantly correlated with sleep efficiency (rs = 0.52) and wake after sleep onset (rs = -0.56). While urinary melatonin metabolite levels did not differ significantly between the groups or menstrual cycle phases, decreased levels during the luteal phase were more prevalent in the underweight group (7 of 10 participants) than in the control group (3 of 13 participants). This study suggests an association between underweight and sleep quality, especially nocturnal awakening, in young females. These findings underscore the importance of considering sleep quality in the management of underweight young females to improve their overall health outcomes.

Dietary palmitic acid to oleic acid ratio modulates energy metabolism and biological rhythms in young healthy Japanese males.

The present study investigated the potential role of the composition of dietary fatty acids in the regulation of biological rhythms, such as the sleep architecture, core body temperature and leukocyte clock gene expression, in subjects fed meals rich in palmitic acid (PA) or oleic acid (OA). Eleven males participated in two sessions of indirect calorimetry in a whole-room metabolic chamber. In each session, subjects consumed three meals rich in PA (44·3 % of total fat as PA and 42·3 % as OA) or OA (11·7 % of total fat as PA and 59·3 % as OA) in the metabolic chamber. The ratio of PA to OA in plasma was significantly lower and fat oxidation was significantly higher during 24 h of indirect calorimetry in the session with meals rich in OA than in that with meals rich in PA. The duration of slow wave sleep (SWS) was shorter, the latency of SWS was longer and the nadir of core body temperature after bedtime was later in the session with meals rich in PA than in that with meals rich in OA. The peak in CRY1 gene expression was earlier and its amplitude was higher in the session with meals rich in PA than in that with meals rich in OA. In healthy young males, meals rich in PA decreased fat oxidation and disrupted biological rhythms, particularly the sleep architecture and core body temperature during sleep, more than meals rich in OA.

Delayed sleep-wake rhythm due to staying at home during the COVID-19 pandemic and sleep debt after returning to campus among Japanese nursing university students: A longitudinal study.

This study aimed to investigate sleep problems during staying at home due to the coronavirus disease 2019 (COVID-19) pandemic and after returning to campus among university nursing students. We analyzed data from self-reported sleep surveys conducted during a nursing course at a university in Tokyo between 2019 and 2021. During staying at home due to COVID-19, we observed delayed sleep-wake rhythm, prolonged sleep duration on weekdays, a decreased sleep debt, improved daytime sleepiness, and worsened insomnia, especially in terms of difficulty initiating sleep (Study 1; 18 paired data). After returning to campus, we found advanced wake-up time, shortened sleep duration, increased sleep debt, worsened insomnia, and increased daytime sleepiness (Study 2; 91 paired data). The association between advanced midpoint of sleep and commute time over an hour (aOR, 3.29; 95%CI: 1.24-8.72) was confirmed. Furthermore, sleep paralysis and nightmares were more prevalent among nursing students with an advanced midpoint of sleep, whereas nursing students whose midpoint of sleep was delayed had higher daytime sleepiness after returning to campus. To maintain regular sleep-wake rhythms and sufficient sleep duration, the educational environment surrounding nursing university students (e.g., curriculum, class schedule, style of class) should be established considering their age-dependent biological rhythm in addition to sleep hygiene education for students.

Effect of Seat Angle when Sleeping in a Car on Quality of Sleep and Its Impact on Calculation Performance the Following Day.

The number of occasions to stay in a car overnight is increasing during disasters; however, the effects on sleep and the impact on daytime functioning are not well understood. We investigated the effect of seat angle when sleeping in a car and its impact on calculation performance the following day. Fifteen healthy males participated in three trials (sleeping in a car with the front seat angled at 45° and 60° in a laboratory and sleeping at home); sleep and calculation performance the following day were compared. Increased wake after sleep onset and decreased slow-wave sleep were observed in the 60° trial, that is, near-vertical, compared with the others. Subjective sleep quality and calculation performance in the 45° and 60° trials were poorer than those in the home trial. The effect of seat angle on sleep was confirmed objectively, but not subjectively, suggesting that a large seat angle might cause sleep impairment.

Changes in sleep behavior, sleep problems, and psychological distress/health-related quality of life of young Japanese individuals before and during the COVID-19 pandemic.

Social restrictions during the coronavirus disease (COVID-19) pandemic have impacted sleep behavior and sleep problems, and their related daytime functioning in young adults. However, no studies have examined such changes in young individuals from countries with mild infection intensity and social restrictions. Therefore, we focused on sleep behaviors and sleep issues in young people in Japan. This study was conducted before and after the pandemic (October 2019 and May 2020, respectively). In total, 2,222 (1,371 students and 851 workers) individuals participated and completed anonymous Web-based questionnaires concerning demographic characteristics, sleep behaviors, sleep problems using the Japanese version of the Epworth Sleepiness Scale (JESS) and the Athens Insomnia Scale (AIS-J), psychological distress using the Japanese version of the Kessler Psychological Distress Scale, and health-related quality of life (HRQoL) evaluated with the Short Form-8 (SF-8). A significantly delayed sleep phase was observed in the second survey compared to the first (p < .001) and was more pronounced in students than in workers (p < .001). The total sleep time, social jetlag degree, and JESS, AIS-J, and SF-8 scores were significantly improved after the pandemic (p < .001, p < .001, p < .001, p < .001, p < .05, and p < .001, respectively). Careful monitoring of whether these modest changes can lead to adjustment concerns is needed.

Sleep-wake rhythm and its association with lifestyle, health-related quality of life and academic performance among Japanese nursing students: a cross-sectional study.

BACKGROUND: Young adults are likely to have activities and go to bed late at night due to their age-dependent delayed endogenous circadian clock. The purpose of the present study was to clarify sleep-wake rhythm and its association with lifestyle, health-related quality of life, and academic performance among nursing students. METHODS: Self-reported questionnaires were distributed to undergraduate nursing students at six universities in Japan. Sleep-wake rhythm was assessed using the morningness-eveningness questionnaire. A quantitative design using the generalized linear mixed effect model was utilized to identify the factors related to the evening type among female nursing students (n = 447). RESULTS: About 18% of the participants were identified as the evening type. Evening type was associated with living alone, part-time job, and club activity. Sleep duration on weekdays was shorter, meal time duration was the shortest, and the percentages of students who skipped meals and those who gained body weight were higher in the evening type than in the morning type and intermediate type. Mental health-related quality of life was lower in the intermediate type and evening type than in the morning type, while there was no difference in physical health-related quality of life among these groups. The percentages of the nursing students who have experienced absence, tardiness, falling asleep during class, and/or interference with academic achievement were higher in the evening type than in other groups. CONCLUSIONS: The present study has important implications for nursing students' biological characteristics and lifestyle, which are associated with their health-related quality of life and academic performance.

Heart rate change and clinical characteristics in patients with neck myoclonus: An observational study.

OBJECTIVE: This study was conducted to evaluate heart rate (HR) change and clinical characteristics in patients with neck myoclonus (NM), a physiological motor phenomenon occurring during sleep. METHODS: For 18 consecutive patients in whom NM was confirmed from video-polysomnography, we analyzed 576 NMs. Change rate of HR at each 1 sec point towards the averaged HR in prior 5 sec period was calculated before and after all NM events. RESULTS: Findings show NM events as more prevalent during REM sleep than during NREM sleep (83.9% vs. 16.1%). For NM without cortical arousal in REM and NREM sleep, the respective HR increased 20 s before NM (p < 0.05); the change rate was up to 13%. For NM with cortical arousal in REM sleep, the HR increased 50 s before NM (p < 0.05); the change rate reached 18%. Three NM subjects showed abnormal vocalization or shouting during REM. Six NM subjects had excessive daytime sleepiness without sleep disorder. CONCLUSION: HR increased before NM events, which may be associated with pathophysiology of NM. NM may possibly be associated with excessive daytime sleepiness or abnormal behaviors during REM sleep. SIGNIFICANCE: HR increase is associated with pathophysiology of NM and clinical symptoms.

The relationship between insomnia symptoms and work productivity among blue-collar and white-collar Japanese workers engaged in construction/civil engineering work: a cross-sectional study.

BACKGROUND: The situation of work productivity loss due to sleep disorders/problems among workers in industrialized societies remains unclear. The purpose of this study was to clarify the prevalence of insomnia symptoms and actual situation of work productivity by job type (white-collars/blue-collars) among construction/civil engineering workers in Japan and evaluate the association between insomnia symptoms and work productivity adjusting for sleep duration and sociodemographic, work-related, and health-related variables. METHODS: This cross-sectional study included 17,828 construction/civil engineering workers (15,837 males and 1991 females) aged 40 to 74 years in Japan. The questionnaire consisted of socio-demographic characteristics, information on work productivity (work performance and absence), respective insomnia symptoms (difficulty initiating sleep; DIS, difficulty maintaining sleep; DMS, and early morning awakening; EMA), bedtime schedule, work-related factors (job type, working hours), and perceived health condition. To identify the associated factors of work productivity, the logistic regression analyses were conducted. RESULTS: The percentages of workers who reported to be experiencing DIS, DMS, and EMA were 7.9, 16.3, and 13.1%, respectively. Poor work performance was associated with every insomnia symptom in both the blue-collar and white-collar workers. Meanwhile, absence was associated with DIS in blue-collar workers and both DIS and DMS in white-collar workers; however, not with EMA in both the groups. In blue-collar workers, engagement in shift work was associated with poor work performance. CONCLUSIONS: The present study revealed the association between insomnia symptoms and work productivity, suggesting the necessity of early prevention of insomnia among both blue-collar and white-collar workers.

Effect of a single bout of morning or afternoon exercise on glucose fluctuation in young healthy men.

The timing of exercise plays an important role in the effect of the exercise on physiological functions, such as substrate oxidation and circadian rhythm. Exercise exerts different effects on the glycemic response to exercise and meal intake depending on when the exercise performed. Here, we comprehensively investigated the effects of the timing (morning or afternoon) of exercise on glucose fluctuation on the basis of several indices: glycemic variability over 24 h (24-h SD), J-index, mean amplitude of glucose excursions (MAGE), continuous overall net glycemic action (CONGA), and detrended fluctuation analysis (DFA). Eleven young men participated in 3 trials in a repeated measures design in which they performed a single bout of exercise at 60% of their maximal oxygen uptake for 1 h beginning either at 7:00 (morning exercise), 16:00 (afternoon exercise), or no exercise (control). Glucose levels were measured using a continuous glucose monitoring system (CGMs). Glucose fluctuation was slightly less stable when exercise was performed in the afternoon than in the morning, indicated by higher CONGA at 2 h and α2 in DFA in the afternoon exercise trial than in the control trial. Additionally, decreased stability in glucose fluctuation in the afternoon exercise trial was supported by the descending values of the other glucose fluctuation indices in order from the afternoon exercise, morning exercise, and control trials. Meal tolerance following exercise was decreased after both exercise trials. Glucose levels during exercise were decreased only in the afternoon exercise trial, resulting in less stable glucose fluctuations over 24 h.

Exercise improves the quality of slow-wave sleep by increasing slow-wave stability.

Exercise can improve sleep by reducing sleep latency and increasing slow-wave sleep (SWS). Some studies, however, report adverse effects of exercise on sleep architecture, possibly due to a wide variety of experimental conditions used. We examined the effect of exercise on quality of sleep using standardized exercise parameters and novel analytical methods. In a cross-over intervention study we examined the effect of 60 min of vigorous exercise at 60% [Formula: see text]max on the metabolic state, assessed by core body temperature and indirect calorimetry, and on sleep quality during subsequent sleep, assessed by self-reported quality of sleep and polysomnography. In a novel approach, envelope analysis was performed to assess SWS stability. Exercise increased energy expenditure throughout the following sleep phase. The subjective assessment of sleep quality was not improved by exercise. Polysomnography revealed a shorter rapid eye movement latency and reduced time spent in SWS. Detailed analysis of the sleep electro-encephalogram showed significantly increased delta power in SWS (N3) together with increased SWS stability in early sleep phases, based on delta wave envelope analysis. Although vigorous exercise does not lead to a subjective improvement in sleep quality, sleep function is improved on the basis of its effect on objective EEG parameters.

Prevalence, clinical symptoms and polysomnographic findings of REM-related sleep disordered breathing in Japanese population.

BACKGROUND: Rapid eye movement sleep -predominant sleep-disordered breathing (REM-SDB) is a condition in which sleep apneas or hypopneas predominantly occur during REM sleep. This study aimed to investigate the prevalence, clinical findings including daytime sleepiness or comorbid cardio-metabolic diseases, and detailed polysomnographic features of REM-SDB in Japanese population. METHODS: Total of 1458 patients diagnosed as SDB were selected for this study. Prevalence of REM-SDB was estimated in the groups of mild, moderate and severe SDB. Polysomnographic findings, daytime sleepiness self-measured with Epworth Sleepiness Scale (ESS) and history of comorbid cardio-metabolic diseases were obtained and compared between the groups with REM-SDB and non-stage specific SDB. RESULTS: Prevalence of REM-SDB according to the criteria #2 was 22.1% in total SDB subjects, 46,1% in mild SDB and 18.9% in moderate SDB. None was found in severe SDB. Patients with REM-SDB showed milder SDB, higher BMI and higher female predominance than those with non-stage specific SDB. They also showed lower arousal index, respiratory arousal index per total AHI, percentage of N1 sleep, total AHI, ODI, and higher sleep efficiency. Meanwhile, maximum event durations of obstructive apnea and hypopnea were significantly longer, and the nadir SpO2 was lower in REM-SDB. The ESS score and percentages of comorbid cardio-metabolic diseases were roughly equivalent between REM-SDB and non-stage specific SDB. CONCLUSION: REM-SDB was associated with high obesity, female gender, and mild severity of SDB. They showed daytime sleepiness and comorbid cardio-metabolic diseases quite equally to patients with non-stage specific SDB in spite of their lower AHI and better sleep quality.

Effects of exercise before breakfast on plasma free fatty acid profile and 24-h fat oxidation.

BACKGROUND: Free fatty acids (FFAs) are an important source of energy, and also serve as signaling molecules to regulate gene expression. Exercise performed in a post-absorptive state, in contrast to that performed in a postprandial state, increases 24-h fat oxidation under an energy-balanced condition. The primary aim of the present study was to clarify whether the effects of exercise on the concentration and composition of plasma FFAs, which may underlie distinct effects of exercise on 24-h fat oxidation, depend on the nutritional state of the individual when performing the exercise. METHODS: Ten healthy young men underwent 3 trials of indirect calorimetry in a metabolic chamber. The subjects performed exercise at 60% of VO2max for 60 min in either a post-absorptive or postprandial state, or remained sedentary without an exercise session (control). All trials were designed to be energy balanced over 24 h. Blood samples were collected immediately before and after exercise. RESULTS: Fat oxidation over 24 h was increased only when exercise was performed in a post-absorptive state (control, 531 ± 60; post-absorptive, 779 ± 70; postprandial, 569 ± 37 kcal/24 h). The increase in the 24-h fat oxidation was related to the magnitude of the transient carbohydrate deficit after exercise. The plasma FFA concentration after exercise was higher in the post-absorptive trial (0.38 ± 0.04) than in the control (0.13 ± 0.01) and postprandial (0.15 ± 0.02 mM) trials. The ratio of unsaturated to saturated (U/S) fatty acids after exercise was higher in the post-absorptive trial (1.76 ± 0.06) than in the control (1.56 ± 0.07) and postprandial (1.53 ± 0.08) trials. On the other hand, the plasma FFA concentration after exercise in a postprandial state did not differ significantly from that in the control trial. CONCLUSION: Exercise performed in a post-absorptive state effectively increased the plasma FFA concentration and U/S ratio to a greater degree than exercise performed in a postprandial state, underlying the increase in the 24-h fat oxidation. The increase in the plasma FFA concentration was related to the transient carbohydrate deficit after exercise.

Skipping Breakfast for 6 Days Delayed the Circadian Rhythm of the Body Temperature without Altering Clock Gene Expression in Human Leukocytes.

Breakfast is often described as "the most important meal of the day" and human studies have revealed that post-prandial responses are dependent on meal timing, but little is known of the effects of meal timing per se on human circadian rhythms. We evaluated the effects of skipping breakfast for 6 days on core body temperature, dim light melatonin onset, heart rate variability, and clock gene expression in 10 healthy young men, with a repeated-measures design. Subjects were provided an isocaloric diet three times daily (3M) or two times daily (2M, i.e., breakfast skipping condition) over 6 days. Compared with the 3M condition, the diurnal rhythm of the core body temperature in the 2M condition was delayed by 42.0 ± 16.2 min (p = 0.038). On the other hand, dim light melatonin onset, heart rate variability, and clock gene expression were not affected in the 2M condition. Skipping breakfast for 6 days caused a phase delay in the core body temperature in healthy young men, even though the sleep-wake cycle remained unchanged. Chronic effects of skipping breakfast on circadian rhythms remain to be studied.

Evaluation of Sleep Quality in a Disaster Evacuee Environment.

We aimed to evaluate sleep and sleep-related physiological parameters (heart rate variability and glucose dynamics) among evacuees by experimentally recreating the sleep environment of evacuation shelters and cars. Nine healthy young male subjects participated in this study. Two interventions, modeling the sleep environments of evacuation shelters (evacuation shelter trial) and car seats (car trial), were compared with sleep at home (control trial). Physiological data were measured using portable two-channel electroencephalogram and electrooculogram monitoring systems, wearable heart rate sensors, and flash glucose monitors. Wake after sleep onset (WASO) and stage shift were greater in both intervention trials than the control trial, while rapid-eye movement (REM) latency and non-rapid eye movement (NREM) 1 were longer and REM duration was shorter in the evacuation shelter trial than the control trial. Glucose dynamics and power at low frequency (LF.p) of heart rate variability were higher in the car trial than in the control trial. It was confirmed that sleep environment was important to maintain sleep, and affected glucose dynamics and heart rate variability in the experimental situation.

Effect of a single bout of exercise on clock gene expression in human leukocyte.

Mammals have circadian clocks, which consist of the central clock in the suprachiasmatic nucleus and the peripheral clocks in the peripheral tissues. The effect of exercise on phase of peripheral clocks have been reported in rodents but not in humans. Continuous sampling is necessary to assess the phase of the circadian rhythm of peripheral clock gene expressions. It has been assumed that the expression of the genes in leukocyte may be "an accessible window to the multiorgan transcriptome." The present study aimed to examine whether exercise affects the level and phase of clock gene expression in human leukocytes. Eleven young men participated in three trials, in which they performed a single bout of exercise at 60% V̇o2max for 1 h beginning either at 0700 (morning exercise) or 1600 (afternoon exercise) or no exercise (control). Blood samples were collected at 0600, 0900, 1200, 1500, 1800, 2100, and 2300 and at 0600 the next morning, to assess diurnal changes of clock gene expression in leukocytes. Brain and muscle ARNT-like protein 1 (Bmal1) expression level increased after morning and afternoon exercise, and Cryptochrome 1 (Cry1) expression level increased after morning exercise. Compared with control trial, acrophase of Bmal1 expression tended to be earlier in morning exercise trial and later in afternoon exercise trial. Acrophase of Cry1 expression was earlier in morning exercise trial but not affected by afternoon exercise. Circadian locomotor output cycles kaput (Clock), Period 1-3 (Per1-3), and Cry2 expression levels and those acrophases were not affected by exercise. The present results suggest a potential role of a single bout of exercise to modify peripheral clocks in humans.NEW & NOTEWORTHY The present study showed that a single bout of exercise affected peripheral clock gene expression in human leukocytes and the effect of exercise depended on when it was performed. Brain and muscle ARNT-like protein 1 (Bmal1) expression was increased after exercises performed in the morning and afternoon. Cryptochrome 1 (Cry1) expression was also increased after the morning exercise. The effect of exercise on acrophase of Bmal1 depended on the time of the exercise: advanced after morning exercise and delayed after afternoon exercise.

Impact of sleep problems on daytime function in school life: a cross-sectional study involving Japanese university students.

BACKGROUND: The aims of this study were 1) to clarify the prevalence of sleep problems (insomnia, insufficient sleep, and delayed sleep-wake phase) among Japanese university students; 2) to examine sociodemographic characteristics, lifestyle, and sleep-related symptoms in each sleep problem; and 3) to evaluate the association between the above-mentioned sleep problems and daytime dysfunction in school life. METHODS: Self-report questionnaire surveys were conducted at eight universities in Japan, and we received 1034 valid answers (78% female). The questionnaire consisted of socio-demographic characteristics, information on lifestyle, sleep pattern, sleep-related symptoms, and daytime dysfunction in school life. Groups with insomnia, behaviorally induced insufficient sleep syndrome (BIISS), delayed sleep-wake phase (DSWP), and BIISS + DSWP were defined. To identify the association between sleep problems and daytime dysfunction in school life, the generalized linear mixed effect model was conducted. RESULTS: Sleep duration on weekdays was 5.9 ± 1.2 h, and 38.2% of the students had a sleep duration < 6.0 h. About 16% of the students were categorized as evening-type individuals. More than half of the students (56.1%) had excessive daytime sleepiness. Insomnia was associated with tardiness (aOR: 0.8, 95%CI: 0.7-0.9) and falling asleep during class (aOR: 1.6: 95%CI: 1.4-2.0). BIISS was associated with tardiness (aOR: 1.5, 95%CI: 1.1-2.2) and interference with academic achievement (aOR: 1.9, 95%CI: 1.3-2.6). DSWP and BIISS + DSWP were associated with absence (aOR: 3.4, 95%CI: 2.2-5.1 / aOR: 4.2, 95%CI: 3.2-5.6), tardiness (aOR: 2.7, 95%CI: 1.8-4.1 / aOR: 2.2, 95%CI: 1.6-2.8), falling asleep during class (aOR: 2.6, 95%CI: 1.4-4.8 / aOR: 7.6, 95%CI: 3.3-17.2), and interference with academic achievement (aOR: 2.6, 95%CI: 1.7-3.9 / aOR: 2.1, 95%CI: 1.6-2.8). CONCLUSIONS: Students with DSWP and BIISS + DSWP were significantly associated with daytime dysfunction in school life, i.e. absence, tardiness, falling asleep during class and interference with academic achievement. Students displaying BIISS + DSWP were considered to have a relatively more serious condition compared with those with only insomnia, DSWP, or BIISS. It is therefore of utmost importance that university students aim to prevent DSWP and BIISS which were associated with daytime function in school life.

Effect of skipping breakfast for 6 days on energy metabolism and diurnal rhythm of blood glucose in young healthy Japanese males.

BACKGROUND: Skipping breakfast has become a common trend that may lead to obesity and type 2 diabetes. Previous studies, which imposed a single incidence of breakfast skipping, did not observe any decrease in 24-h energy expenditure. Furthermore, the effects of breakfast skipping on diurnal blood glucose profiles over 24 h are contradictory. OBJECTIVE: The aim of this study was to clarify the influence of 6 consecutive days of breakfast skipping and sedentary behavior on energy metabolism and glycemic control. METHODS: Ten young men participated in 2 trials (with or without breakfast) that lasted for 6 consecutive days, and the 2 trials were conducted 1 wk apart with a repeated-measures design. During the meal intervention, each subject's blood glucose was measured using the continuous glucose monitoring system. If breakfast was skipped, subjects ate large meals at lunch and dinner such that the 24-h energy intake was identical to that of the 3-meal condition. At 2200 on the fifth day, the subjects entered a room-sized respiratory chamber, where they remained for 33 h, and were instructed to carry out sedentary behavior. RESULTS: The glucose levels were similar between the 2 meal conditions during the first 5 d of meal intervention, but the blood glucose at 2300 was higher in the breakfast-skipping condition than in the 3-meal condition. Breakfast skipping elevated postprandial glycemic response after lunch on the first day of meal intervention. On the sixth day, there were no significant differences in 24-h energy expenditure and substrate oxidation. When subjects remained in a metabolic chamber, the level of physical activity significantly decreased, glycemic stability slightly deteriorated, and mean blood glucose over 24 h was higher in the breakfast-skipping trial than in the 3-meal trial. CONCLUSIONS: Sedentary lifestyle and repeated breakfast skipping caused abnormal glucose fluctuations, whereas 24-h energy metabolism remained unaffected. Clinical Trial Registry: This trial was registered at http://www.umin.ac.jp/english/ as UMIN000032346.

Clinical significance of social jetlag in patients with excessive daytime sleepiness.

Social jetlag has recently attracted attention as the circadian misalignment between biological and social clocks. We aimed to examine social jetlag and its effect on daytime sleepiness and daily functions in patients with narcolepsy, behaviorally induced insufficient sleep syndrome (BIISS) and delayed sleep-wake phase disorder (DSPD). The levels of social jetlag (SJLmid) and sleep-corrected social jetlag (SJLsc) were calculated for each patient, and the effect of these social jetlag-related parameters on daytime sleepiness and daily functions were examined. Objective sleepiness measured by the mean sleep latency in the multiple sleep latency test, subjective sleepiness assessed by the Epworth sleepiness scale (ESS), health-related quality of life (HRQoL) assessed by the SF-8 health survey, and incidences of mistakes in daily activities, traffic accidents and near-miss events related to daytime sleepiness were compared among the narcolepsy (n = 39), BIISS (n = 87) and DSPD (n = 28) groups. Both SJLmid and SJLsc showed a negative correlation with physical HRQoL in patients with narcolepsy and a positive correlation with the ESS score in patients with DSPD. In patients with BIISS, SJLsc reflected sleep loss rather than circadian misalignment; moreover, SJLsc was not associated with daytime sleepiness and daily functions. Social jetlag was not associated with incidences of mistakes in daily activities, traffic accidents and near-miss events. The state of social jetlag and its association with daily functions differed among the narcolepsy, BIISS and DSPD groups. Social jetlag represented sleep debt in BIISS, circadian misalignment in narcolepsy and both in DSPD. Our results thus show that the clinical manifestations and significance of social jetlag differ depending on the underlying sleep disorders.