Ambient coarse particulate matter and hospital admissions in the medicare cohort air pollution study, 1999–2010

Background: In recent years a number of studies have examined the short-term association between coarse particulate matter (PM_10–2.5) and mortality and morbidity outcomes. These studies, however, have produced inconsistent conclusions. Objectives: We estimated both the national- and regional-level associations between PM_10–2.5 and emergency hospitalizations for both cardiovascular and respiratory disease among Medicare enrollees ≥ 65 years of age during the 12-year period 1999 through 2010. Methods: Using air pollution data obtained from the U.S. Environmental Protection Agency air quality monitoring network and daily emergency hospitalizations for 110 large urban U.S. counties assembled from the Medicare Cohort Air Pollution Study (MCAPS), we estimated the association between short-term exposure to PM_10–2.5 and hospitalizations using a two-stage Bayesian hierarchical model and Poisson log-linear regression models. Results: A 10-μg/m³ increase in PM_10–2.5 was associated with a significant increase in same-day cardiovascular hospitalizations [0.69%; 95% posterior interval (PI): 0.45, 0.92]. After adjusting for PM_2.5, this association remained significant (0.63%; 95% PI: 0.38, 0.88). A 10-μg/m³ increase in PM_10–2.5 was not associated with a significant increase in respiratory-related hospitalizations. Conclusions: We found statistically significant evidence that daily variation in PM_10–2.5 is associated with emergency hospitalizations for cardiovascular diseases among Medicare enrollees ≥ 65 years of age. This association was robust to adjustment for concentrations of PM_2.5.