Particulate Matter and Incident Chronic Kidney Disease in Japan: The Ibaraki Prefectural Health Study (IPHS).

Introduction: Global health hazards caused by air pollution, such as chronic kidney disease (CKD), have been gaining attention; however, air pollution-associated CKD has not been explored in Japan.

Methods: We examined 77,770 men and women with estimated glomerular filtration rate (eGFR) ≥60 ml/min/1.73 m² in the Ibaraki Prefecture who participated in annual community-based health checkups from 1993 at 40-75 years old and were followed up through December 2020. The outcome was newly developed kidney dysfunction with eGFR of <60 ml/min/1.73 m² during follow-up. To assess air pollution, a PM_2.5 exposure model was employed to estimate yearly means at 1 × 1-km resolution, converted into means at the municipal level. Hazard modeling was employed to examine PM_2.5 concentrations in residential areas as a risk factor for outcomes.

Results: Participants were distributed across 23 municipalities in the Ibaraki Prefecture, with PM_2.5 concentrations between 16.2 and 33.4 μg/m³ (mean, 22.7 μg/m³) in 1987-1995 as the exposure period. There were 942 newly developed kidney dysfunctions during follow-up. Based on 1987-1995 PM_2.5 concentrations as the baseline exposure, the multivariate-adjusted hazard ratio per 10-μg/m³ increase in PM_2.5 for newly developed kidney dysfunction was 1.02 (95%CI, 0.80-1.24) in men and 1.19 (95%CI, 0.95-1.44) in women.

Conclusions: Elevated PM_2.5 did not represent a significant risk factor for incident CKD in a prefecture in Japan.