Association between sleep characteristics and physical functioning in middle-aged and elderly adults: findings from...

Aging is associated with declines in muscle strength and physical function, and sleep plays a crucial role in maintaining musculoskeletal health. This cohort study, based on the China Health and Retirement Longitudinal Study (CHARLS), aims to explore the relationship between sleep characteristics and physical performance in middle-aged and elderly individuals.

A total of 2,998 participants from the CHARLS cohort were included, with baseline data from the 2011 survey and follow-up data from the 2015 survey. Nighttime sleep and napping patterns were assessed, and changes in sleep duration over time were categorized. Physical functioning was assessed through handgrip strength, the chair stand test, the walking test, appendicular skeletal muscle mass, and SPPB scores. Multiple linear regression and restricted cubic spline models were employed to analyze the effects of sleep patterns on muscle health.

After adjusting for all confounding factors, multifactor liner regression indicated that napping durations exceeding 90 min were associated with reduced grip strength (β = -0.39, 95% CI: -1.43, -0.01, P < 0.05) and longer chair stand test times (β = 0.59, 95% CI: 0.18, 0.99, P < 0.01). The restricted cubic spline indicated a clear U-shaped relationship between nap duration and grip strength (non-linear P < 0.05), whereas no such relationship was observed between nap duration and performance on the chair stand test. In subgroup analyses addressing significant confounding factors, it was found that participants older than 65 years, males, and those with low levels of daily activity exhibited greater sensitivity to the effects of sleep on physical function. The joint analysis showed that compared to individuals with less than 6 h of nighttime sleep and no napping, those with 6-8 h of nighttime sleep and 30-90 min of napping exhibited longer chair stand test durations (β = 0.63, 95% CI: 0.06, 1.20, P < 0.05). Additionally, individuals with 6-8 h of nighttime sleep and naps exceeding 90 min showed longer walking times (β = 1.44, 95% CI: 0.68, 2.21, P < 0.01).

Both insufficient and excessive nighttime sleep at baseline were linked to diminished physical performance. For older adults, a nap duration approximately 50 min may be potentially optimal for maintaining grip strength. These findings highlight the importance of proper sleep management, particularly for men over 65 years old with low activity levels, in preserving physical function and reducing the risk of mobility decline.