Association between circadian syndrome and frailty progression among middle-aged and older adults in China: A longitudinal study based on CHARLS.

BACKGROUND: Frailty is a significant predictor of adverse outcomes. Circadian syndrome (CircS), a cluster of cardiometabolic risk factors linked to circadian disruption, may interact with frailty; however, evidence for this relationship remains limited. METHODS: A total of 7330 participants from the China Health and Retirement Longitudinal Study (CHARLS) were included. CircS was defined by seven components. Frailty was measured by the frailty index (FI). Group-based trajectory modeling (GBTM) was employed to identify different frailty trajectories. Multinomial logistic regression models were conducted to assess the association between baseline CircS status and frailty trajectories. Linear mixed-effects models were used to examine the association between the number of baseline CircS components and the subsequent rate of change in FI over time. RESULTS: Three frailty trajectories were identified: low-stable frailty (n = 4670, 63.71%), moderate-rising frailty (n = 2109, 28.77%), and high-stable frailty (n = 551, 7.52%). Compared to participants without CircS, those with CircS at baseline had a significantly higher risk of belonging to the moderate-rising trajectory (RRR = 2.48, 95% CI: 2.17, 2.84, p < 0.001) and the high-stable trajectory (RRR = 4.37, 95% CI: 3.51, 5.45, p < 0.001). Furthermore, participants with 4, 5, and ≥ 6 CircS components had greater annual increases in FI, with additional increases of 0.0022 (95% CI: 0.0011, 0.0033, p < 0.001), 0.0020 (95% CI: 0.0007, 0.0033, p < 0.01), and 0.0033 (95% CI: 0.0016, 0.0049, p < 0.001) per year, respectively, compared with those with <4 components. CONCLUSIONS: This study showed that baseline CircS status was significantly associated with unfavorable frailty trajectories, while a greater CircS component burden was associated with both higher baseline FI levels and a faster subsequent increase in FI. These findings highlight the potential relevance of CircS for identifying individuals at increased risk of adverse frailty outcomes.