Depressive symptoms and incident chronic lung disease: a three- cohort cross-national comparison of 117,160 adults from China, the United States, and Europe

Depression has long been viewed as a consequence of chronic lung disease (CLD), but emerging evidence suggests it may also precede its onset. Whether this association holds across national contexts, which symptom dimensions drive it, and how depressive symptom trajectories modify risk remain unresolved. We addressed these questions by pooling harmonized data from three nationally representative prospective cohorts: the China Health and Retirement Longitudinal Study (CHARLS), the Health and Retirement Study (HRS), and the Survey of Health, Ageing and Retirement in Europe (SHARE). In total, 117,160 adults free of CLD and asthma at baseline were followed, generating 9,275 incident CLD events. Depressive symptoms were assessed with the CES-D (CHARLS, HRS) and EURO-D (SHARE), which use different cutoffs and are not directly equated across cohorts. Cox proportional hazards models adjusted for age, sex, smoking, education, BMI, diabetes, heart disease, stroke, and alcohol, and random-effects meta-analysis estimated hazard ratios (HRs) and 95% confidence intervals (CIs). In a separate trajectory analysis using the first three waves as the exposure period and subsequent waves as follow-up, participants were classified into five trajectory groups. After full adjustment, baseline depressive symptoms were associated with a broadly consistent ~ 50% higher CLD risk across all three countries (CHARLS HR = 1.55, 95% CI: 1.41–1.71; HRS HR = 1.56, 95% CI: 1.43–1.69; SHARE HR = 1.52, 95% CI: 1.42–1.61; pooled HR = 1.54, 95% CI: 1.48–1.60; I² = 0%). In the subtype analysis, both somatic and cognitive-affective symptoms were independently associated with incident CLD, with somatic symptoms showing slightly stronger effect sizes. In the trajectory analysis (n = 57,241), participants with persistently high depressive symptoms during the exposure period had a 2.1- to 3.0-fold higher CLD risk during subsequent follow-up, while those with decreasing symptoms showed an attenuated but still elevated risk. These findings provide cross-national evidence that both somatic and cognitive-affective depressive symptoms are associated with incident CLD, and that persistently elevated symptoms confer the greatest risk across China, the United States, and Europe.