An intensive longitudinal examination of daily physical activity and sleep in midlife women.

Objectives: Previous research examining physical activity (PA) and sleep link has largely ignored the day-to-day variability that is present in these 2 health behaviors, and few studies have addressed this relation using objective assessments of PA and sleep. Through an intensive longitudinal design, the present study aimed: (1) to elucidate the reciprocal associations between PA and sleep; and (2) to better understand the role of body mass index (BMI) in these 2 health behaviors.

Methods: Community-dwelling midlife women (N = 103; M = 53, age range= 40-60 years) wore an accelerometer for the objective assessment of PA and sleep for 21 days. A series of multilevel models were estimated to test concurrent and lagged associations between PA (activity counts, moderate-to-vigorous PA) and sleep (total sleep time [TST], sleep efficiency, sleep fragmentation indices).

Results And Conclusions: In concurrent, same-day analyses, a positive association emerged between PA and sleep such that as activity counts increased during the day, TST at night also increased (P < .05). In lagged analyses examining next-day effect of sleep on PA, a negative association was found such that greater TST on a given night was associated with less moderate-to-vigorous PA the subsequent day (P < .05). A moderation effect by BMI was also observed such that women with a high BMI engaging in overall lower levels of PA demonstrated poorer-quality sleep. The data suggest that leading a physically active lifestyle may have protective effects on sleep, particularly for overweight and obese women.