Effect modification by cardiovascular and metabolic disease onset on long-term PM exposure and mortality: a nationwide cohort study.

Cardiovascular and metabolic diseases-specifically myocardial infarction, congestive heart failure, cerebrovascular disease, peripheral vascular disease, renal disease, and liver disease-are major public health concerns worldwide. However, studies examining how these diseases modify the relationship between long-term PM exposure and mortality remain scarce. Using a Cox regression model with a population-representative cohort from South Korea, we estimated the modifying effects of six major cardiovascular and metabolic diseases on PM-mortality association in two cohorts: (1) individuals without underlying diseases (NoUD) and (2) those with only hypertension and/or diabetes (HTN/DM). The interaction between PM and each disease onset was used to estimate effect modification, with results presented as relative hazard ratios (RHRs) per 10 µg/m increase in PM. Among 183,834 subjects, non-accidental deaths occurred in 18.0% of the NoUD (N = 134,584) and 25.7% of the HTN/DM (N = 49,250). In the NoUD cohort, renal disease (RHR: 1.58; 95% CI: 1.27-1.97), myocardial infarction (1.41; 1.15-1.73), and liver disease (1.40; 1.25-1.57) significantly modified the effect of PM on mortality. In the HTN/DM cohort, renal disease (1.74; 1.43-2.12), myocardial infarction (1.62; 1.29-2.05), and cerebrovascular disease (1.32; 1.17-1.51) showed higher RHRs. Our findings highlight the importance of consistent and preemptive care for renal disease and myocardial infarction and provide evidence for target-specific interventions to reduce the risk of PM on mortality.