Sleep timing and metabolic health in midlife womenTaylor, Briana (2017) Sleep timing and metabolic health in midlife women. Master's Thesis, University of Pittsburgh. (Unpublished)
AbstractCircadian 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 timing was associated with either measure of metabolic health in prospective analyses. These data indicate that individual differences in sleep timing are associated with metabolic health in a non-shift working population. The current findings provide support for a chronobiological model linking sleep timing with metabolic health. Share
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