Is sleep timing related to objectively measured physical activity and sedentary behavior in older women?

Purpose: Sleep, sedentary behavior, and physical activity are the components of the 24-hour model, while the timing of sleep may play a critical role to impact waking behaviors. Therefore, the present study aimed to examine the relationship of sleep timing with sedentary behavior, light-intensity, moderate-to-vigorous-intensity physical activity, and daily steps in older women. Patients and Methods: A total of 90 community-dwelling older women (70.5 ± 5.4 years) were included in our sample. Multiple linear regression models were used to estimate the associations of accelerometer-measured sedentary behavior and physical activity metrics with the three sleep timing indicators (bedtime and wake time, and mid-sleep time). Bedtime and wake time were recorded by the participants, and mid-sleep time was estimated based on the two sleep indicators. Results: Most indicators of sleep timing were negatively associated with moderate-to-vigorous-intensity physical activity (unstandardized coefficient [B]−0.07 for bedtime and mid-sleep time, p<0.05) and daily steps (B ranged from −15.51 for bedtime to −13.73 for wake time, p<0.05). No associations of sleep timing were found in sedentary behavior and light-intensity physical activity. Conclusion: The findings suggest that sleep timing should be considered when designing promising strategies or interventions for older women to be physically active.