Abstract: Context: Shift work, which imposes a habitual disruption in the circadian system, has been linked to increased incidence of cardiometabolic diseases, and acute circadian misalignment alters various metabolic processes. However, it remains unclear whether day-to-day circadian dysregulation contributes to these risks beyond poor sleep and other behavioral characteristics. Objective: Individuals differ in circadian phase preference, known as chronotype, but may be constrained by modern work obligations to specific sleep schedules. Individuals experience social jetlag (SJL) due to a habitual discrepancy between their endogenous circadian rhythm and actual sleep times imposed by social obligations. Here, we examined whether chronotype and/or SJL associate with components of cardiovascular disease risk beyond the known effects of sleep disturbances, poor health behaviors, and depressive symptomatology. Design: Participants were healthy, midlife adults who worked part- or full-time day shifts (n = 447; mean age,...

Abstract: Context: Chronotype is a trait determining individual circadian preference in behavioral and biological rhythm relative to external light-dark cycle. However, little is known about the relationship between chronotype and metabolic disorders. Objective: The aim of this study was to examine whether late chronotype is related to metabolic abnormalities and body composition in middle-aged adults, independent of sleep duration and lifestyle. Design and Participants: A total of 1620 participants aged 47–59 years were recruited from the Korean Genome and Epidemiology Study. Main Outcome Measures: Chronotype was assessed by the Morningness-Eveningness Questionnaire. Associations of chronotype with diabetes, metabolic syndrome, sarcopenia, and visceral obesity were analyzed. All participants underwent the oral glucose tolerance test, and body composition was measured with dual energy x-ray absorptiometry. Visceral obesity was designated as visceral fat area, measured by abdominal computed tomography, of >100 cm2. ...

Abstract: Several studies have shown the differences among chronotypes in the circadian rhythm of different physiological variables. Individuals show variation in their preference for the daily timing of activity; additionally, there is an association between chronotype and sleep duration/sleep complaints. Few studies have investigated sleep quality during the week days and weekends in relation to the circadian typology using self-assessment questionnaires or actigraphy. The purpose of this study was to use actigraphy to assess the relationship between the three chronotypes and the circadian rhythm of activity levels and to determine whether sleep parameters respond differently with respect to time (weekdays versus the weekend) in Morning-types (M-types), Neither-types (N-types) and Evening-types (E-types). The morningness–eveningness questionnaire (MEQ) was administered to 502 college students to determine their chronotypes. Fifty subjects (16 M-types, 15 N-types and 19 E-types) were recruited to undergo a 7-days ...

Abstract: The dim light melatonin onset (DLMO) is the most reliable measure of central circadian timing in humans. However, it is not always possible to measure the DLMO because sample collection has to occur in the hours before usual sleep onset, it requires staff support and considerable participant effort, and it is relatively expensive. Questionnaires that ask people about the timing of their behavior, such as their sleep, may provide an easier and less expensive estimate of circadian timing. The objective of this analysis was to compare the MEQ score derived from the Morningness-Eveningness Questionnaire (MEQ) and the MSFsc derived from the Munich ChronoType Questionnaire (MCTQ) to the DLMO in the largest sample to date (N = 60). Our hypothesis was that MSFsc would correlate more highly with the DLMO than MEQ score. Our sample of 36 healthy controls and 24 patients with delayed sleep phase disorder ranged in age from 18 to 62 years. All participants slept at times of their own choosing for a week before the assessment of their DLMO. The DLMO correlated significantly with both the MEQ score (r = -0.70, p < 0.001) and MSFsc (r = 0.68, p < 0.001). A linear regression using MEQ, MSFsc, and age to predict the DLMO explained 60% of the DLMO variance. The strongest predictor of the DLMO was MSFsc (beta = 0.51, p = 0.001), followed by MEQ (beta = -0.41, p = 0.004), and age (beta = 0.26, p = 0.013). The beta values for MSFsc and MEQ score were not statistically different from each other. Nonetheless, around a 4-h range in the DLMO was observed at a given MEQ score and a given MSFsc, indicating that neither questionnaire should be exclusively used to time light or exogenous melatonin treatment, as this could result in the mistiming of these treatments relative to the DLMO, thereby potentially worsening circadian misalignment.

Abstract: Associations among late chronotype, body mass index and dietary behaviors in young adolescents

Abstract: Purpose of reviewTo highlight the recent findings on sleep–obesity associations in children. We focus on sleep duration, sleep timing and chronotype, and describe the potential mechanisms underlying sleep–obesity associations.Recent findingsPoor sleep is increasingly common in children and associati

Abstract: Our lives are structured by the daily alternation of activity and rest, of wake and sleep. Despite significant advances in circadian and sleep research, we still lack answers to many of the most fundamental questions about this conspicuous behavioral pattern. We strongly believe that investigating this pattern in entrained conditions, real-life and daily contexts— in situ —will help the field to elucidate some of these central questions. Here, we present two common approaches for in situ investigation of human activity and rest: the Munich ChronoType Questionnaire (MCTQ) and actimetry. In the first half of this chapter, we provide detailed instructions on how to use and interpret the MCTQ. In addition, we give an overview of the main insights gained with this instrument over the past 10 years, including some new findings on the interaction of light and age on sleep timing. In the second half of this chapter, we introduce the reader to the method of actimetry and share our experience in basic analysis techniques, including visualization, smoothing, and cosine model fitting of in situ recorded data. Additionally, we describe our new approach to automatically detect sleep from activity recordings. Our vision is that the broad use of such easy techniques in real-life settings combined with automated analyses will lead to the creation of large databases. The resulting power of big numbers will promote our understanding of such fundamental biological phenomena as sleep.

Abstract: Night shift work has been classified as a probable human carcinogen based on experimental studies and limited human evidence on breast cancer. Evidence on other common cancers, such as prostate cancer, is scarce. Chronotype is an individual characteristic that may relate to night work adaptation. We evaluated night shift work with relation to prostate cancer, taking into account chronotype and disease severity in a population based case-control study in Spain. We included 1,095 prostate cancer cases and 1,388 randomly selected population controls. We collected detailed information on shift schedules (permanent vs. rotating, time schedules, duration, frequency), using lifetime occupational history. Sociodemographic and lifestyle factors were assessed by face-to-face interviews and chronotype through a validated questionnaire. We used unconditional logistic regression analysis adjusting for potential confounders. Subjects who had worked at least for one year in night shift work had a slightly higher prostate cancer risk [Odds Ratio (OR) 1.14; 95%CI 0.94, 1.37] compared with never night workers; this risk increased with longer duration of exposure (≥28 years: OR 1.37; 95%CI 1.05, 1.81; p-trend = 0.047). Risks were more pronounced for high risk tumors [D'Amico classification, Relative Risk Ratio (RRR) 1.40; 95%CI 1.05, 1.86], particularly among subjects with longer duration of exposure (≥28 years: RRR 1.63; 95%CI 1.08, 2.45; p-trend = 0.027). Overall risk was higher among subjects with an evening chronotype, but also increased in morning chronotypes after long-term night work. In this large population based study, we found an association between night shift work and prostate cancer particularly for tumors with worse prognosis.

Abstract: Objective. Although sleep is a biomarker for general health and pathological conditions, its changes across age and gender are poorly understood.Methods. Subjective evaluation of sleep was assessed by questionnaires in 5,064 subjects, and 2,966 were considered without sleep disorders. Objective evaluation was performed by polysomnography in 2,160 subjects, and 1,147 were considered without sleep disorders. Only subjects without sleep disorders were included (aged 40–80 years).Results. Aging was strongly associated with morning preference. Older subjects, especially women, complained less about sleepiness, and pathological sleepiness was significantly lower than in younger subjects. Self-reported sleep quality and daytime functioning improved with aging. Sleep latency increased with age in women, while sleep efficiency decreased with age in both genders. Deep slow-wave sleep decreased with age, but men were more affected. Spectral power densities within slow waves (< 5 Hz) and fast spindles (14–14.75 Hz) d...

Abstract: Poor sleep quality has been demonstrated to diminish cognitive performance, impair psychosocial functioning and alter the perception of stress. At present, however, there is little understanding of how sleep quality affects emotion processing. The aim of the present study was to determine the extent to which sleep quality, measured through the Pittsburg Sleep Quality Index, influences affective symptoms as well as the interaction between stress and performance on an emotional memory test and sustained attention task. To that end, 154 undergraduate students (mean age: 21.27 years, standard deviation = 4.03) completed a series of measures, including the Pittsburg Sleep Quality Index, the Sustained Attention to Response Task, an emotion picture recognition task and affective symptom questionnaires following either a control or physical stress manipulation, the cold pressor test. As sleep quality and psychosocial functioning differ among chronotypes, we also included chronotype and time of day as variables of interest to ensure that the effects of sleep quality on the emotional and non-emotional tasks were not attributed to these related factors. We found that poor sleep quality is related to greater depressive symptoms, anxiety and mood disturbances. While an overall relationship between global Pittsburg Sleep Quality Index score and emotion and attention measures was not supported, poor sleep quality, as an independent component, was associated with better memory for negative stimuli and a deficit in sustained attention to non-emotional stimuli. Importantly, these effects were not sensitive to stress, chronotype or time of day. Combined, these results suggest that individuals with poor sleep quality show an increase in affective symptomatology as well as a negative cognitive bias with a concomitant decrease in sustained attention to non-emotional stimuli.

Abstract: The study aimed to test whether a shift in chronotype (determined by mid-sleep on free days) is associated with alterations in psychological well-being and sleep parameters. One hundred and seventeen undergraduates were tested in longitudinal study with four repeated measures. Measurements were taken during spring in three-week intervals and each measurement consisted of self-reported sleep parameters on work and free days (i.e. bedtime, sleep latency, wake time, sleep onset, mid-sleep time, social jetlag), satisfaction with life, and mood (energetic arousal, tense arousal, hedonic tone). Between-subjects analyses revealed earlier chronotypes, as compared to the later ones, showing lower tense arousal, higher energetic arousal and life satisfaction, earlier bedtime, sleep onset and offset on both work and free days, longer sleep duration and shorter sleep latency on workdays, and less social jetlag. Within-subjects analyses revealed increasing photoperiod associated with a shift toward earlier chronotype,...

Abstract: In this commentary (which is by no means a review of chronotyping), I try to clarify the distinction between 2 different ways of assessing chronotype by questionnaires. The morningness/eveningness questionnaire (MEQ) determines daily preferences producing a score, and the Munich ChronoType Questionnaire aims to determine phase of entrainment producing a time. An understanding of the MEQ requires knowledge of its history. Although both have their respective validity, they mean very different things and should be used appropriately in studies with different aims and questions. Although they show correlations in population comparisons, they should not be amalgamated when reviewing the literature.

Abstract: Background and aimM.R. present address: PAIN, National Institutes of Health, Bethesda, MD, USACluster headache (CH) is the headache disorder with the strongest chronobiological traits. The severe attacks of pain occur with diurnal and annual rhythmicity but the precise rhythm and involvement of potential zeitgebers is unknown. Patients complain of poor sleep quality yet this has never been studied. We investigated triggers, rhythms, sleep quality and chronotypes in CH.MethodsPatients and controls completed questionnaires and structured interviews composed of new and previously validated parts including the Pittsburgh Sleep Quality Index (PSQI) and Morningness-Eveningness Questionnaire (MEQ). Patients were characterized by a CH index, a unified measure of headache burden.ResultsA total of 275 CH patients and 145 matched controls were included. The most common trigger was sleep (80%) and a relationship between clusters and daylight was identified. Of the patients, 82.2% reported diurnal and 56% annual rhyth...

Abstract: Circadian clocks of adolescents typically run late-including sleep times-yet adolescents generally are expected at school early in the morning. Due to this mismatch between internal (circadian) and external (social) times, adolescents suffer from chronic sleep deficiency, which, in turn, affects academic performance negatively. This constellation affects students' future career prospects. Our study correlates chronotype and examination performance. In total, 4734 grades were collected from 741 Dutch high school students (ages 11-18 years) who had completed the Munich ChronoType Questionnaire to estimate their internal time. Overall, the lowest grades were obtained by students who were very late chronotypes (MSFsc > 5.31 h) or slept very short on schooldays (SDw < 7.03 h). The effect of chronotype on examination performance depended on the time of day that examinations were taken. Opposed to late types, early chronotypes obtained significantly higher grades during the early (0815-0945 h) and late (1000-1215 h) morning. This group difference in grades disappeared in the early afternoon (1245-1500 h). Late types also obtained lower grades than early types when tested at the same internal time (hours after MSFsc), which may reflect general attention and learning disadvantages of late chronotypes during the early morning. Our results support delaying high school starting times as well as scheduling examinations in the early afternoon to avoid discrimination of late chronotypes and to give all high school students equal academic opportunities.

Abstract: A great body of research indicates that eveningness is associated with negative psychological outcomes, including depressive and anxiety symptoms, behavioral dyscontrol and different health impairing behaviors. Impaired subjective sleep quality, increased circadian misalignment and daytime sleepiness were also reported in evening-type individuals in comparison with morning-types. Although sleep problems were consistently reported to be associated with poor psychological functioning, the effects of sleep disruption on the relationship between eveningness preference and negative emotionality have scarcely been investigated. Here, based on questionnaire data of 756 individuals (25.5% males, age range = 18–43 years, mean = 25.3 ± 5.8 years), as well as of the evening-type (N = 211) and morning-type (N = 189) subgroups, we examined the relationship among sleep problems, eveningness and negative emotionality. Subjects completed the Hungarian Version of the Horne and Ostberg Morningness–Eveningness Questionnaire...

Abstract: Circadian rhythms and sleep patterns change as people age. Little is known about the associations between circadian rhythms and mortality rates. We investigated whether 24-hour activity rhythms and sleep characteristics independently predicted mortality. Actigraphy was used to determine the stability and fragmentation of the 24-hour activity rhythm in 1,734 persons (aged 45-98 years) from the Rotterdam Study (2004-2013). Sleep was assessed objectively using actigraphy and subjectively using sleep diaries to estimate sleep duration, sleep onset latency, and waking after sleep onset. The mean follow-up time was 7.3 years; 154 participants (8.9%) died. Sleep measures were not related to mortality after adjustment for health parameters. In contrast, a more stable 24-hour activity rhythm was associated with a lower mortality risk (per 1 standard deviation, hazard ratio = 0.83, 95% confidence interval: 0.71, 0.96), and a more fragmented rhythm was associated with a higher mortality risk (per 1 standard deviation, hazard ratio = 1.22, 95% confidence interval: 1.04, 1.44). Low stability and high fragmentation of the 24-hour activity rhythm predicted all-cause mortality, whereas estimates from actigraphy and sleep diaries did not. Disturbed circadian activity rhythms reflect age-related alterations in the biological clock and could be an indicator of disease.

Abstract: The behavioral trait of preference to schedule the daily activities for morning or evening hours forms a continuum, with the anchorage ends of “early birds” and “night owls,” and is called chronotype. Genetic effects contribute to the chronotype by about half and the other half is accounted for non-shared environmental effects. However, no “chronotype gene” has been identified yet. There is a growing body of literature on health hazards that has been attributed to the chronotype itself, being independent of a number of factors. So far, without any exception, of those health hazards that do differ between the chronotypes, all have been more common among the “night owls” than among the “early birds,” such as mood disorders, anxiety disorders, substance use disorders, personality disorders, insomnia, sleep apnea, arterial hypertension, bronchial asthma, type 2 diabetes, and infertility. Alarmingly, current data suggest that “night owls” tend to die younger than “early birds”.

Abstract: Diurnal preference (chronotype) is a useful instrument for studying circadian biology in humans. It harbours trait-like dimensions relating to circadian period and sleep homeostasis, but also has ontogenetic components (morningness increases with age). We used the Morningness-Eveningness questionnaire (MEQ) in the Baependi study, a family-based cohort study based in a small town in Minas Gerais, Brazil. The population is highly admixed and has a cohesive and conservative lifestyle. 825 individuals (497 female) aged 18–89 years (average ± SD = 46.4 ± 16.3) and belonging to 112 different families participated in this study. The average MEQ score was 63.5 ± 11.2 with a significant (P < 0.0001) linear increase with age. Morningness was significantly (P < 0.0001) higher in the rural (70.2 ± 9.8) than in the municipal zone (62.6 ± 11.1), and was also significantly (P = 0.025) higher in male (64.6 ± 10.9) than in female (62.8 ± 11.2) participants. Thus, in spite of universal access to electricity, the Baependi population was strongly shifted towards morningness, particularly in the rural zone. Heritability of MEQ score was 0.48 when adjusted for sex and age, or 0.38 when adjusted for sex, age, and residential zone. The reported MEQ score heritability is more akin to those of previous twin studies than previous family studies.

Abstract: Background & Aims Sleep disturbance is associated with the development of obesity, diabetes and hepatic steatosis in murine models. Hepatic triglyceride accumulation oscillates in a circadian rhythm regulated by clock genes, light-dark cycle and feeding time in mice. The role of the sleep-wake cycle in the pathogenesis of human non-alcoholic fatty liver disease (NAFLD) is indeterminate. We sought to detail sleep characteristics, daytime sleepiness and meal times in relation to disease severity in patients with NAFLD. Methods Basic Sleep duration and latency, daytime sleepiness (Epworth sleepiness scale), Pittsburgh sleep quality index, positive and negative affect scale, Munich Chronotype Questionnaire and an eating habit questionnaire were assessed in 46 patients with biopsy-proven NAFLD and 22 healthy controls, and correlated with biochemical and histological parameters. Results In NAFLD compared to healthy controls, time to fall asleep was vastly prolonged (26.9 vs. 9.8 min., p = 0.0176) and sleep duration was shortened (6.3 vs. 7.2 hours, p = 0.0149). Sleep quality was poor (Pittsburgh sleep quality index 8.2 vs. 4.7, p = 0.0074) and correlated with changes in affect. Meal frequency was shifted towards night-times (p = 0.001). In NAFLD but not controls, daytime sleepiness significantly correlated with liver enzymes (ALAT [r = 0.44, p = 0.0029], ASAT [r = 0.46, p = 0.0017]) and insulin resistance (HOMA-IR [r = 0.5, p = 0.0009]) independent of cirrhosis. In patients with fibrosis, daytime sleepiness correlated with the degree of fibrosis (r = 0.364, p = 0.019). Conclusions In NAFLD sleep duration was shortened, sleep onset was delayed and sleep quality poor. Food-intake was shifted towards the night. Daytime sleepiness was positively linked to biochemical and histologic surrogates of disease severity. The data may indicate a role for sleep-wake cycle regulation and timing of food-intake in the pathogenesis of human NAFLD as suggested from murine models.

Abstract: While important changes in circadian rhythms take place during adolescence and young adulthood, it is unclear how circadian profiles during this period relate to emerging mental disorders. This study aimed to: (i) characterise morningness-eveningness preference in young people with primary anxiety, depression, bipolar or psychotic disorders as compared to healthy controls, and (ii) to investigate associations between morningness-eveningness preference and the severity of psychiatric symptoms. Four hundred and ninety-six males and females aged between 12 and 30 years were divided into five groups according to primary diagnosis. The Hamilton Depression Rating Scale and the Brief Psychiatric Rating Scale were administered by a research psychologist and participants completed the Kessler Psychological Distress Scale and the Horne-Ostberg Morningness-Eveningness Questionnaire (ME). ME scores were significantly lower (i.e. higher levels of "eveningness") in all patient diagnosis subgroups compared to the control group. The psychosis group had higher ME scores than the depression and anxiety groups. Compared to the control group, the anxiety, depression and bipolar subgroups had a significantly higher proportion of "moderate evening" types, with a similar trend for the psychosis group. The proportion of "extreme evening" types was significantly higher in the anxiety and depression subgroups than in the control group. Lower ME scores correlated with worse psychological distress in males from the bipolar group. Lower ME scores correlated with higher depression severity in females with depression and in males with bipolar disorder. These results suggest that young persons with various mental disorders, especially those with affective disorders, present with a stronger "eveningness" preference and higher rates of evening chronotypes than healthy controls from the same age group. Later chronotypes were generally associated with worse psychological distress and symptoms severity. These associations were modulated by sex and primary diagnosis.