Data from a five-year sleep study involving 161 Caucasian, 121 African American and 56 Chinese non-shift working women aged 48-58 has found that going to bed later, and having greater variability in bedtime, were associated with higher insulin resistance, and greater bedtime advance (going to bed earlier) was associated with higher body mass index (BMI).
Changes in bedtime, and later bedtimes, were partly due to shifts in bedtime at the weekend.
Diabetes risk increases in midlife women, and this finding suggests that irregular sleep schedules may be an important factor. Metabolic health was better in women who had more regular sleep schedules, including regular bedtimes across weekdays and weekends."
Taylor BJ, Matthews KA, Hasler BP, Roecklein KA, Kline CE, Buysse DJ, Kravitz HM, Tiani AG, Harlow SD, Hall MH. Bedtime variability and metabolic health in midlife women: the SWAN Sleep Study. SLEEP 2016;39(2):457–465.