Association of PM2.5 changes with advanced kidney disease progression and mortality in patients with early CKD: a nationwide retrospective cohort study in Taiwan

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. This retrospective cohort study enrolled 472,141 early CKD patients (stages 1–3a) between 2012 and 2022, with follow-up through 2023. 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 were used to 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 . Kaplan–Meier method was used to compare event-free survival among the tertile groups. Restricted cubic spline analysis was performed to characterize the concentration–response relationship. Subgroup analyses evaluated whether predefined patient characteristics modified these associations. Each 1 µg/m³ reduction in PM 2.5 was associated with 5%, 3%, and 6% lower risks of advanced CKD progression, dialysis initiation, and mortality, respectively. Compared with the reference tertile, participants in the most improved tertile exhibited 34%, 17%, and 36% lower risks, whereas those in the most deteriorated tertile had 1.31-, 1.02-, and 1.28-fold higher risks. Spline analyses indicated near-linear relationships, with protective effects attenuated beyond a 7 µg/m³ reduction in PM 2.5 . Kaplan–Meier curves demonstrated a significant, dose-dependent decrease in event-free survival across higher PM 2.5 tertiles ( P trend < 0.001). Subgroup analyses revealed that each 1 µg/m³ reduction in PM₂.₅ was consistently associated with greater risk reductions across all outcomes among males and individuals with monthly incomes ≤ NT$21,900. Improvements in PM 2.5 exposure are associated with reduced risks of advanced CKD progression, dialysis initiation, and mortality among early CKD patients. Males and individuals with lower incomes consistently demonstrated more pronounced protective effects associated with PM₂.₅ reduction. Public health strategies promoting air quality may represent effective early interventions to protect kidney health, particularly among populations vulnerable to PM₂.₅-related kidney injury.