Effects of a yearlong moderate-intensity exercise and a stretching intervention on sleep quality in postmenopausal women

Study Objectives: To examine the effects of a moderate-intensity exercise or stretching intervention and changes in fitness, body mass index, or time spent outdoors on self-reported sleep quality and to examine the relationship between the amount and timing of exercise and sleep quality. Design: A randomized intervention trial. Setting: A cancer research center in Seattle, Washington. Participants: Postmenopausal, overweight or obese, sedentary women not taking hormone replacement therapy, aged 50 to 75 years, and recruited from the Seattle metropolitan area. Interventions: A yearlong moderate-intensity exercise (n=87) and a low-intensity stretching (n=86) program. Measurements and Results: Among morning exercisers, those who exercised at least 225 minutes per week had less trouble falling asleep (odds ratio [OR]: 0.3, P less than or equal to .05) compared with those who exercised less than 180 minutes per week. However, among evening exercisers, those who exercised at least 225 minutes per week had more trouble falling asleep (OR: 3.3, P less than or equal to .05) compared to those who exercised less than 180 minutes per week. Stretchers were less likely to use sleep medication (OR=0.4, P less than or equal to .05) and have trouble falling asleep (OR: 0.7, P less than or equal to .10) during the intervention period compared with baseline. A greater than 10% versus a 1% or less increase in maximum O-2 consumption over the year was associated with longer sleep duration (P less than or equal to .05), less frequently falling asleep during quiet activities (P less than or equal to .05), and less use of sleep medication (P less than or equal to .05). Reductions in body mass index and increases in time spent outdoors had inconsistent effects on sleep quality. Conclusions: Both stretching and exercise interventions may improve sleep quality in sedentary, overweight, postmenopausal women. Increased fitness was associated with improvements in sleep. However, the effect of moderate-intensity exercise may depend on the amount of exercise and time of day it is performed.