Consistent Sleep Schedules May be Important for Metabolic Health

A new study from the American Academy of Sleep Medicine suggests that irregular bedtime schedules in midlife could be related to negative metabolic health among non-shift working women.

The findings, published in the February issue of Sleep [1], looked at data from the Study of Women’s Health Across the Nation (SWAN) Sleep Study. It involved 161 Caucasian, 121 African American and 56 Chinese, non-shift working women. The age range of participants was between 48 and 58 years. The women kept daily journals that were used to gauge four types of sleep timing, including mean bedtime, bedtime variability, bedtime delay and bedtime advance.

Insulin resistance and body mass index (BMI) were measured at the beginning of the study and again an average of five years later.

Read more: What You Eat May Influence Sleep Quality [2]

“Irregular sleep schedules, including highly variable bedtimes and staying up much later than usual are associated in midlife women with insulin resistance, which is an important indicator of metabolic health, including diabetes risk,” lead author Martica Hall, Ph.D., professor of psychiatry at the University of Pittsburgh said in a prepared statement. “We found that weekday-weekend differences in bedtime were especially important.”

The study found that women who stayed up, for example, two hours later on weekends than their usual work week, was associated with an increase in insulin resistance five years later. The association was only significant when both weekdays and weekends were included in the analysis. According to the researchers, large differences in bedtime between work days and personal days were important in the association of impaired glucose regulation.

The researchers said that sleeping and waking at different times could change the amount of light the body is exposed to, which is an important cue for keeping the body’s circadian clock in rhythm. A disruption in the circadian timing may harm glucose metabolism and energy homeostasis.

“The results are important because diabetes risk increases in midlife women,” Hall said. “Our study suggests that irregular sleep schedules may be an important piece of this puzzle. The good news is that sleep timing is a modifiable behavior. Metabolic health was better in women who had more regular sleep schedules, including regular bedtimes across weekdays and weekends.”

This research was funded by the National Institutes of Health.