Impact of Long-Term Exposures to Ambient PM2.5 and Ozone on ARDS Risk for Older Adults in the United States

BACKGROUND: Chronic exposures to particulate matter with an aerodynamic diameter < 2.5 mu m (PM2.5) and ozone pollution can affect respiratory function. ARDS, an often lethal respiratory failure, is most common among older adults. However, few epidemiology studies have investigated an association between air pollution and the risk of ARDS. METHODS: This observational study was conducted to estimate air pollution exposures at the ZIP code level and hospital admissions with ARDS among US Medicare beneficiaries aged >= 65 years from 2000 to 2012. A two-pollutant generalized linear mixed model, adjusting for sex, age, race, median household income, smoking, and weather, was applied. RESULTS: There were a total of 1,164,784 hospital admissions with ARDS in the cohort. Increases of 1 mu g/m(3) in annual average PM2.5 and of 1 parts per billion in annual average ozone were associated with increases in annual hospital admission rates for ARDS of 0.72% (95% CI, 0.62-0.82) and 0.15% (95% CI, 0.08-0.22), respectively. In low-pollution regions (annual average PM2.5 level < 12 mu g/m(3) and annual average ozone level < 45 parts per billion), the same annual increase in PM2.5 and ozone were associated with increases in annual hospital admission rates for ARDS of 1.50% (95% CI, 1.27-1.72) and 0.27% (95% CI, 0.16-0.38). CONCLUSIONS: Long-term exposures to PM2.5 and ozone were associated with increased risk of ARDS among older adults in the United States, including exposures below current annual US National Ambient Air Quality Standards.