Circadian syndrome is associated with adverse ADL and IADL functional trajectories among middle-aged and older adults in China

Circadian syndrome (CircS) captures metabolic, sleep and depressive symptom clustering, but its link with long-term functional trajectories remains unclear. To examine associations of CircS with activities of daily living (ADL) and instrumental activities of daily living (IADL) limitation trajectories and their heterogeneity. This cohort study used data from the China Health and Retirement Longitudinal Study (2011–2020). Participants were community-dwelling adults aged ≥ 45 years. The baseline sample included 6,598 participants; trajectory analyses included 5,550 (ADL) and 5,558 (IADL) with ≥ 3 follow-up waves. CircS was operationalized using a seven-component definition previously applied in CHARLS studies; this research definition is not a validated clinical diagnostic tool. ADL and IADL limitation trajectories (2013–2020) were identified using latent class growth models. Multinomial logistic regression and causal forest models were used. Of 6,598 participants, 2,481 (37.6%) had CircS; mean age was 58.98 years; 3,316 (50.3%) were women. After adjustment, CircS was associated with higher odds of ADL late deterioration (OR 1.36, 95% CI 1.13–1.64) and mid‑period high limitation (OR 1.30, 95% CI 1.03–1.64). CircS was also associated with higher odds of IADL late deterioration (OR 1.67, 95% CI 1.35–2.08), mid‑period high limitation (OR 2.02, 95% CI 1.54–2.65) and progressive deterioration (OR 1.36, 95% CI 1.11–1.68). Causal forest analysis showed that CircS was associated with higher probabilities of worse ADL and IADL trajectories (absolute differences: +4.81 [95% CI 2.25–7.73] and + 8.32 [95% CI 5.68–10.91] percentage points, respectively). CircS was associated with worse ADL and IADL functional trajectories, with more consistent associations for IADL. CircS may represent a potential risk marker associated with long-term functional decline.