Associations between physical activity trajectories and circadian syndrome among middle-aged and older adults in China

Circadian syndrome (CircS) is associated with multiple adverse health outcomes. Physical activity (PA) is a key modifiable behavior in middle-aged and older adults, yet evidence linking it to CircS remains limited. This study aimed to examine the relationship between physical activity trajectories and CircS. Using data from the China Health and Retirement Longitudinal Study (CHARLS; 2011–2015), PA was assessed using the IPAQ-SF, and trajectories were identified using group-based trajectory modeling (GBTM). Multivariable logistic regression examined the associations of PA trajectories with prevalent CircS and its seven individual components. Subgroup analyses were stratified by sociodemographic and behavioral characteristics, with interactions tested. To provide more detailed evidence, PA levels in 2015 were additionally examined as a supplementary cross-sectional analysis, focusing on current PA intensity, frequency, duration, and volume in relation to prevalent CircS. Restricted cubic spline (RCS) models assessed dose–response relationships, with sensitivity and subgroup analyses conducted. Among 1,488 participants, four PA trajectories were identified: Stable low (12.4%), Stable middle (40.0%), Stable high (40.7%), and High-decreasing with modest rebound (6.9%). After full adjustment, the Stable middle, Stable high, and High-decreasing with modest rebound trajectories were associated with a reduced risk of CircS compared with the Stable low trajectory, with ORs of 0.62 (95% CI: 0.43–0.87), 0.40 (95% CI: 0.27–0.57), and 0.46 (95% CI: 0.27–0.77), respectively. Subgroup analysis showed that the high-PA group was generally associated with a lower risk of CircS than the low-to-moderate PA group across most subgroups. Component-specific analyses showed that the Stable High trajectory was associated with lower odds of all seven CircS components, whereas the other trajectories were associated only with selected metabolic components. In the supplementary PA-level analysis, VPA, MPA, or LPA ≥ 3 days/week; VPA or MPA 10–29 min/day or LPA ≥ 30 min/day; and VPA, MPA, or LPA ≥ 150 min/week were inversely associated with CircS compared with sedentary reference groups, with adjusted ORs ranging from 0.38 for VPA 10–29 min/day (95% CI: 0.14–0.93) to 0.75 for MPA ≥ 150 min/week (95% CI: 0.59–0.95). RCS analyses demonstrated a linear inverse dose–response relationship between TPA and CircS risk, with similar patterns observed for several CircS components. This study identified four distinct PA trajectories among middle-aged and older adults in China and found that, compared with the Stable Low trajectory, the Stable Middle, Stable High, and High-decreasing with modest rebound trajectories were associated with lower odds of CircS. The supplementary PA level analysis further showed that higher PA levels were also associated with lower odds of CircS compared with the sedentary reference groups. Public health strategies should incorporate physical activity into primary prevention measures for CircS among middle-aged and older adults.