Associations between long term air pollution exposure and first hospital admission for kidney and total urinary system diseases in the US Medicare population: nationwide longitudinal cohort study

Abstract

OBJECTIVE To estimate the associations between long term exposure to air pollution and the first hospital admission related to kidney and total urinary system diseases. DESIGN Nationwide longitudinal cohort study. SETTING Data were collected from the Medicare fee-for-service for beneficiaries living in 34849 zip codes across the continental United States from 2000 to 2016. Exposure variables were annual averages of traffic related pollutants (fine particles (PM2.5) and nitrogen dioxide (NO2)) that were assigned according to the zip code of residence of each beneficiary with the use of validated and published hybrid ensemble prediction models. PARTICIPANTS All beneficiaries aged 65 years or older who were enrolled in Medicare part A fee-for-service (n=61097767). PRIMARY AND SECONDARY OUTCOME MEASURES First hospital admission with diagnosis codes for total kidney and urinary system disease or chronic kidney disease (CKD), analyzed separately. RESULTS The average annual concentrations of air pollution were 9.8 mu g/m(3) for PM2.5 and 18.9 ppb for NO2. The total number of first admissions related to total kidney and urinary system disease and CKD were around 19.0 million and 5.9 million, respectively (2000-16). For total kidney and urinary system disease, hazard ratios were 1.076 (95% confidence interval 1.071 to 1.081) for a 5 mu g/m(3) increase in PM2.5 and 1.040 (1.036 to 1.043) for a 10 ppb increase in NO2. For CKD, hazard ratios were 1.106 (1.097 to 1.115) for a 5 mu g/m(3) increase in PM2.5 and 1.013 (1.008 to 1.019) for a 10 ppb increase in NO2. These positive associations between PM2.5 and kidney outcomes persisted at concentrations below national health based air quality standards. CONCLUSIONS The findings suggest that higher annual air pollution levels were associated with increased risk of first hospital admission related to diseases of the kidney and urinary system or CKD in the Medicare population.