Circadian rest-activity rhythms and physical function in community-dwelling older men: The MrOS sleep study

Circadian rest-activity rhythms (RARs) reflect ones' physical activity and sleep patterns over the 24-hour day, correlating with cardiometabolic risk, fall risk, and cognitive decline. Physical function also declines with advancing age, leading to disability and increased risk of mortality. Thus, we examined the associations between rest-activity rhythms and physical function in older men.

In the Osteoporotic Fractures in Men (MrOS) study, 2924 men (age = 76.3±5.5 years old, 90% white) completed the sleep ancillary study (baseline) with valid wrist-worn accelerometry data and physical function measures. Physical function measures included the following: 6-meter gait speed, chair stand speed, and grip strength, assessed at baseline and up to 4 follow-up visits over 6.4±3.9 years. Using 3 approaches to quantify rest-activity rhythms (functional principal components analysis, parametric, and non-parametric approaches), we evaluated cross-sectional and longitudinal associations between baseline rest-activity rhythm patterns and decline in physical function using mixed-effects models, adjusting for demographic, lifestyle, and medical covariates.

Less strength of rest-activity rhythm (ie, principal component 1, amplitude, and relative amplitude) and lower regularity (pseudo-F statistic) were both cross-sectionally and longitudinally associated with poorer physical function, particularly with gait speed and chair stand speed. Yet, significant associations between timing-related rest-activity rhythm exposures and chair stand speed were only observed cross-sectionally. Overall, the magnitude of associations differed slightly across rest-activity rhythm estimation approaches and more substantially by physical function measures.

Rest-activity rhythms might be a potential risk modifiable factor to target for intervention in future studies if aiming to maintain better physical function, particularly lower extremity function.