Starting off the day with a brisk walk or even a light stretching routine can help post-menopausal women sleep better at night, according to new research from the Public Health Sciences Division.
In a study of overweight, sedentary women ages 50 to 75, Dr. Anne McTiernan and colleagues found that women who exercised at a moderate intensity for at least half an hour every morning fell asleep easier at night than those who exercised less. Women who performed evening exercises experienced little or no improvement in sleep onset or quality.
"Postmenopausal women commonly report sleep problems," McTiernan said. "Exercise may help to alleviate these problems, as long as it is performed early in the day."
The analysis-the largest and longest of its kind-was part of the Physical Activity for Total Health Study, which is investigating the effect of a yearlong moderate-intensity exercise program compared to a stretching program on various health parameters, including breast-cancer risk and changes in body-mass index and immune-system function.
Researchers randomly assigned participants to one of two physical-activity groups. The moderate-exercise group completed five weekly sessions that included 45 minutes of cardiovascular activity such as treadmill walking or stationary bicycling. Women assigned to the stretching group performed a 60-minute stretching and relaxation session each week and were encouraged to do an additional 15- to 30-minute session at home three times each week. Participants completed questionnaires before the study began and at three-month intervals that included questions about their sleep quality.
Timing is everything
Researchers found physical activity-whether moderately intensive cardiovascular exercise or simply stretching-associated with better sleep quality. However, the benefit only occurred in women who exercised early in the day.
It isn't yet known why the timing of exercise affects sleep quality, but McTiernan speculates that hormone levels are a factor.
"Exercise could affect some hormones that keep you more awake," she said "In the morning, those energizing hormones make you feel good during the day. By the time night falls, they'll have worn off and you can sleep better."
The study appears in the November issue of SLEEP. Co-authors include Dr. Shelley Tworoger, Dr. Yutaka Yasui, Dr. Cornelia Ulrich, Erin Aiello, Dr. Deborah Bowen and Dr. John Potter, all of PHS, and colleagues at the University of Washington, the University of Colorado Health Sciences Center, Yale University School of Medicine and Group Health Cooperative's Center for Health Studies in Seattle.