Long-term ozone exposure and mortality in patients with chronic kidney disease: a large cohort study

Epidemiologic studies on the effects of long-term exposure to ozone (O₃) have shown inconclusive results. It is unclear whether to O₃ has an effect on chronic kidney disease (CKD). We investigated the effects of O₃ on mortality and renal outcome in CKD.

We included 61,073 participants and applied Cox proportional hazards models to examine the effects of ozone on the risk of end-stage renal disease (ESRD) and mortality in a two-pollutants model adjusted for socioeconomic status. We calculated the concentration of ozone exposure one year before enrollment and used inverse distance weighting (IDW) for interpolation, where the exposure was evenly distributed.

In the single pollutant model, O₃ was significantly associated with an increased risk of ESRD and all-cause mortality. Based on the O₃ concentration from IDW interpolation, this moving O₃ average was significantly associated with an increased risk of ESRD and all-cause mortality. In a two-pollutants model, even after we adjusted for other measured pollutants, nitrogen dioxide did not attenuate the result for O₃. The hazard ratio (HR) value for the district-level assessment is 1.025 with a 95% confidence interval (CI) of 1.014-1.035, while for the point-level assessment, the HR value is 1.04 with a 95% CI of 1.035-1.045. The impact of ozone on ESRD, hazard ratio (HR) values are, 1.049(95%CI: 1.044-1.054) at the district unit and 1.04 (95%CI: 1.031-1.05) at the individual address of the exposure assessment. The ozone hazard ratio for all-cause mortality was 1.012 (95% confidence interval: 1.008-1.017) for administrative districts and 1.04 (95% confidence interval: 1.031-1.05) for individual addresses.

This study suggests that long-term ambient O₃ increases the risk of ESRD and mortality in CKD. The strategy to decrease O₃ emissions will substantially benefit health and the environment.