Prospective association between circadian syndrome and incident chronic lung disease in the CHARLS and ELSA cohorts.

Circadian syndrome (CircS) involves the integration of systemic circadian disruption with cardiometabolic risk factors, but its longitudinal effect on incident chronic lung disease (CLD) remains unknown. This prospective dual-cohort study analyzed data from the China Health and Retirement Longitudinal Study (CHARLS, n = 7,553) and the English Longitudinal Study of Ageing (ELSA, n = 4,957). CircS was defined by the clustering of at least 4 out of 7 circadian-metabolic components. Multivariate Cox proportional hazards models estimated hazard ratios (HRs) for incident CLD over a seven-year follow-up. In the discovery cohort (CHARLS), CircS was independently associated with an increased risk of incident CLD (HR = 1.16, 95% CI = 1.01-1.33). This was robustly confirmed in the validation cohort (ELSA) with a stronger effect size (HR = 1.53, 95% CI = 1.20-1.95). Furthermore, subgroup analyses revealed that this risk was significantly amplified by alcohol consumption in the British population (P < 0.05), suggesting an interactive effect between circadian misalignment and lifestyle stressors. In conclusion, CircS serves as a robust, independent predictor of respiratory decline. Evaluating circadian integrity offers a reliable indicator of respiratory vulnerability, and holistic chronomedicine approaches targeting sleep hygiene and moderate alcohol consumption may help mitigate the global CLD burden.