The association between long-term ambient fine particulate exposure and the mortality among adult patients initiating dialysis: A retrospective population-based cohort study in Taiwan

Fine particulate matter (PM2.5) has been reported to be associated with increased risk of chronic kidney disease (CKD) and progression to end-stage renal disease (ESRD). However, studies on whether long-term exposure to PM2.5 negatively impacts the survival of patients with ESRD are very limited. To conduct this study, we linked Taiwan Air Quality-Monitoring Database (TAQMD) and the National Health Insurance Research Database (NHIRD) by zip-code. A retrospective population-based cohort of 34,088 adult patients initiating dialysis over six months was formed. Cox proportional regression models were used to estimate the risk of mortality in dialysis patients per 10-μg/m3 increase of PM2.5 and by PM2.5 levels divided into quintiles. Restricted cubic spline analysis was performed to delineate the concentration-response relationship between PM2.5 and mortality. The adjusted hazard ratio (aHR) per 10-μg/m3 increase of PM2.5 for mortality was 1.11 (95% confidence interval [CI] = 1.08-1.13). When analyzing PM2.5 exposure divided into quintiles, patients with mean PM2.5 exposure over 29.33 μg/m3, including level III (aHR 1.00, 95% CI = 0.94-1.07), level IV (aHR 1.09; 95% CI = 1.03-1.16), and level V (HR 1.11; 95% CI = 1.05-1.19), were at stepwise higher risks of mortality compared with level I. Spline analysis showed a non-linear concentration-response function between PM2.5 and mortality, with the lowest mortality aHR identified at a mean PM2.5 of 26 μg/m3, followed by a concentration interval with a gradual increase of aHR, and finally a steep rise of mortality risk when mean PM2.5 exceeded 37 μg/m3. Individuals with older age, those were male, with selected comorbidities, and with low socioeconomic status (SES) were at higher mortality risk. Male and non-diabetics participants were more sensitive to the effect of a 10-μg/m3 of PM2.5 increase on mortality than their counterparts. In conclusion, long-term exposure to PM2.5 exceeding a threshold was observed to be associated with increased risk of mortality among dialysis patients.