Reduction in ambient PM2.5 associated with decreased risk of dialysis and mortality among patients with advanced chronic kidney disease: A population-based retrospective cohort study in Taiwan

Fine particulate matter (PM_2.5) is associated with the development of chronic kidney disease (CKD). However, studies validating the beneficial effects of reducing ambient PM_2.5 levels on CKD remain limited. The Taiwan government has implemented 'Clean Air Action Plans' since 2015. We aim to investigate the effects of changes in PM_2.5 on dialysis incidence and mortality among patients with advanced CKD. This retrospective population-based cohort study recruited 31,027 patients with CKD stage 3b to 5 during 2016-2020 and followed them until December 31, 2021. The change in PM_2.5 (ΔPM_2.5) was defined by subtracting the 365-day mean concentration before the index date from that before the end of follow-up. Cox regression models were used to assess the hazard of dialysis incidence and mortality per 1-μg/m³ reduction in PM_2.5, as well as by dividing ΔPM_2.5 into tertiles. Restricted cubic spline analysis was performed to delineate the concentration-response relationship between ΔPM_2.5 and the outcomes. We observesed that each 1-μg/m³ reduction in ambient PM_2.5 was associated with an 11 % decrease in dialysis incidence and a 14 % decrease in mortality risk. Patients in tertile 1 (with improved PM_2.5) experienced a reduced risk of outcomes (hazard ratio for dialysis, 0.70; 95 % confidence interval, 0.65-0.75), while those in tertile 3 (with deteriorated PM_2.5) had an increased risks compared to those in tertile 2. An approximately linear relationship between ΔPM_2.5 and risk of outcomes was observed. In conclusion, improvement in ambient PM_2.5 levels is significantly associated with a reduced risk of dialysis and mortality among advanced CKD patients.