Association of PM2.5 Changes with Advanced Kidney Disease Progression and Mortality in Patients with Early CKD: A Nationwide Retrospective Cohort Study in Taiwan

Background Fine particulate matter (PM _2.5 ) is an increasingly recognized risk factor for kidney disease. However, evidence on the kidney-protective effects of improvements in PM _2.5 exposure is limited. Early intervention in chronic kidney disease (CKD) is essential. We aimed to explore the association of changes in long-term PM _2.5 exposure with advanced CKD progression and mortality among early-stage CKD patients. Methods This retrospective cohort study enrolled 423,855 early CKD patients (stages 1–3a) between 2012 and 2021, with follow-up through 2022. PM _2.5 change (ΔPM _2.5 ) was defined as the difference between the 365-day mean concentration before enrollment and the 365-day mean before follow-up end. Multivariate Cox proportional hazards models assessed associations of ΔPM _2.5 with advanced CKD progression, dialysis initiation, and mortality, both per 1 µg/m³ change and across tertiles of ΔPM _2.5 . Restricted cubic spline analyses characterized concentration-response relationships. Results Each 1 µg/m³ reduction in PM _2.5 was associated with 8%, 5%, and 7% lower risks of advanced CKD progression, dialysis initiation, and mortality, respectively. Compared with the reference tertile, participants in the most improved tertile exhibited 19%, 9%, and 28% lower risks, whereas those in the most deteriorated tertile had 2.25-, 1.59-, and 1.94-fold higher risks. Spline analyses indicated near-linear relationships, with protective effects in CKD progression and mortality plateauing beyond a 15 µg/m³ reduction. Conclusions Improvements in PM _2.5 exposure are associated with reduced risks of advanced CKD progression, dialysis initiation, and mortality among early CKD patients. Public health strategies promoting air quality may represent effective early interventions to protect kidney health.