Impact of change in bedtime variability on body composition and inflammation: Secondary findings from the Go Red for Women Strategically Focused Research Network

Variability in daily sleep patterns is an emerging factor linked to metabolic syndrome. However, whether reducing bedtime variability improves markers of disease risk has not been tested. Here, we assessed whether body composition and inflammation were impacted by changes in bedtime variability over a 6-wk period, during which, women were instructed to maintain healthy, habitual sleep patterns (one arm of a randomized trial). Data were available for 37 women (age 34.9±12.4 y, BMI 24.7±2.9 kg/m(2), sleep duration 7.58±0.49 h/night). Body composition and leukocyte platelet aggregates (LPA) were measured at baseline and endpoint using magnetic resonance imaging and flow cytometry, respectively. Sleep data were collected weekly using wrist actigraphy. Change in bedtime variability was calculated as the difference in the standard deviation of bedtimes measured during the 2-wk screening period and the 6-wk intervention period. Results showed that women who reduced their bedtime variability (n=29) during the intervention had reductions in total (P<0.001) and subcutaneous adipose tissue (P<0.001) relative to women who increased/maintained (n=8) bedtime variability. Similar effects were observed for LPA levels between women who reduced vs increased/maintained bedtime variability (P=0.011). Thus, reducing bedtime variability, without changing sleep duration, could improve cardiometabolic health by reducing adiposity and inflammation.