Air Pollution and Acute Kidney Injury in the U.S. Medicare Population: A Longitudinal Cohort Study

BACKGROUND: Recent studies have reported the association between air pollution exposure and reduced kidney function. However, it is unclear whether air pollution is associated with an increased risk of acute kidney injury (AKI). OBJECTIVES: To address this gap in knowledge, we investigated the effect estimates of long-term exposures to fine particulate matter [PM [Formula: see text] in aerodynamic diameter ([Formula: see text])], nitrogen dioxide ([Formula: see text]), and ozone ([Formula: see text]) on the risk of first hospital admission for AKI using nationwide Medicare data. METHODS: This nationwide population-based longitudinal cohort study included 61,300,754 beneficiaries enrolled in Medicare Part A fee-for-service (FFS) who were [Formula: see text] years of age and resided in the continental United States from the years 2000 through 2016. We applied Cox-equivalent Poisson models to estimate the association between air pollution and first hospital admission for AKI. RESULTS: Exposure to [Formula: see text] , [Formula: see text] , and [Formula: see text] was associated with increased risk for first hospital admission for AKI, with hazard ratios (HRs) of 1.17 (95% CI: 1.16, 1.19) for a [Formula: see text] increase in [Formula: see text] , 1.12 (95% CI: 1.11, 1.13) for a [Formula: see text] increase in [Formula: see text] , and 1.03 (95% CI: 1.02, 1.04) for a [Formula: see text] increase in summer-period [Formula: see text] (June to September). The associations persisted at annual exposures lower than the current National Ambient Air Quality Standard. DISCUSSION: This study found an association between exposures to air pollution and the risk of the first hospital admission with AKI, and this association persisted even at low concentrations of air pollution. Our findings provide beneficial implications for public health policies and air pollution guidelines to alleviate health care expenditures and the disease burden attributable to AKI. https://doi.org/10.1289/EHP10729