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Evening chronotype is strongly associated with greater alcohol use, though mechanisms underlying this association are not well understood. Difficulties with emotion regulation may be involved. Evening chronotypes report less emotional stability and are at increased risk for psychopathology associated with poor emotional control. The current study evaluated chronotype differences in emotion regulation using a standardized laboratory task and evaluated emotion regulation as a potential mechanism linking evening chronotype and alcohol use. Eighty-one undergraduates from the University of Pittsburgh were studied. Chronotype was assessed using the Composite Scale of Morningness. Alcohol use was reported daily using an online diary and the Alcohol Use Disorder Identification Test (AUDIT). Participants completed an emotion regulation task, within two hours of their habitual wake-time, wherein they attempted to down-regulate negative and up-regulate positive emotions while viewing emotionally-charged images. Self-reported affect, heart rate variability (HF-HRV), and pre-ejection period (PEP) were measured throughout the task. Thirty-one evening chronotypes were compared to 50 intermediate chronotypes. Evening chronotypes reported significantly greater symptoms of alcohol use disorder (F = 4.399, p = 0.039). There were no chronotype differences in self-reported affect, HF-HRV, or PEP during the emotion regulation task. Longer sleep duration on non-free days was associated with increased HF-HRV during negative emotion regulation among intermediate chronotypes. Earlier testing sessions were associated with increased HF-HRV during negative emotion regulation among evening chronotypes. Moderated mediation revealed that emotion regulation did not mediate the association between evening chronotype and alcohol use, irrespective of sleep duration on non-free days or time of testing session. This study adds to the body of literature by demonstrating that undergraduate evening chronot

Evening chronotype is strongly associated with greater alcohol use, though mechanisms underlying this association are not well understood. Difficulties with emotion regulation may be involved. Evening chronotypes report less emotional stability and are at increased risk for psychopathology associated with poor emotional control. The current study evaluated chronotype differences in emotion regulation using a standardized laboratory task and evaluated emotion regulation as a potential mechanism linking evening chronotype and alcohol use. Eighty-one undergraduates from the University of Pittsburgh were studied. Chronotype was assessed using the Composite Scale of Morningness. Alcohol use was reported daily using an online diary and the Alcohol Use Disorder Identification Test (AUDIT). Participants completed an emotion regulation task, within two hours of their habitual wake-time, wherein they attempted to down-regulate negative and up-regulate positive emotions while viewing emotionally-charged images. Self-reported affect, heart rate variability (HF-HRV), and pre-ejection period (PEP) were measured throughout the task. Thirty-one evening chronotypes were compared to 50 intermediate chronotypes. Evening chronotypes reported significantly greater symptoms of alcohol use disorder (F = 4.399, p = 0.039). There were no chronotype differences in self-reported affect, HF-HRV, or PEP during the emotion regulation task. Longer sleep duration on non-free days was associated with increased HF-HRV during negative emotion regulation among intermediate chronotypes. Earlier testing sessions were associated with increased HF-HRV during negative emotion regulation among evening chronotypes. Moderated mediation revealed that emotion regulation did not mediate the association between evening chronotype and alcohol use, irrespective of sleep duration on non-free days or time of testing session. This study adds to the body of literature by demonstrating that undergraduate evening chronot

Circadian rhythms are critical to health and functioning. Circadian misalignment can result from desynchrony between sleep-wake cycles and the natural light-dark cycle, disrupting time-dependent variations in biological functioning associated with metabolism and energy homeostasis. Here, we test a chronobiological model suggesting that sleep timing may act on health outcomes via a melatonergic-metabolic pathway by gating the effect of light on circadian signaling. We evaluated associations between four measures of sleep timing and indices of metabolic health in order to assess the importance of sleep timing for healthy functioning in midlife women. Participants were 338 Caucasian (n = 161), African American (n = 121) and Chinese (n = 56) women who participated in the SWAN Sleep Study and who were not taking insulin or other insulin-related medications. Participants reported habitual sleep-wake times in the Pittsburgh Sleep Diary for a minimum of 11 nights. From self-reported sleep-wake times, four measurements of sleep timing were calculated: average bedtime, variability in bedtime, bedtime delay, and social jetlag. Body mass index (BMI) and the homeostasis model assessment of insulin resistance (HOMA-IR) were measured at two time points (average years between time points = 5.39 ± 0.71). We expected later average bedtime, greater variability in bedtime, more bedtime delay, and more social jetlag to be associated with higher BMI and higher HOMA-IR at time one and time two. Greater variability in bedtime was associated with higher HOMA-IR at Time 1 after controlling for race, menopausal status, sleep duration, exercise, depression, and BMI (β = .132; p = .005). Moreover, fully adjusted cross-sectional models also revealed significant positive associations between bedtime delay and both BMI (β = .128; p < .001) and HOMA-IR (β = .098; p = .038). Average bedtime and social jetlag were unrelated to metabolic health in cross-sectional analyses and no measure of sleep timin