PM_2.5 and hospital admissions among Medicare enrollees with chronic debilitating brain disorders

Background: Although long-term exposure to particulate matter<2.5 μm (PM_2.5) has been linked to chronic debilitating brain disorders (CDBD), the role of short-term exposure in health care demand, and increased susceptibility for PM_2.5-related health conditions, among Medicare enrollees with CDBD has received little attention. We used a causal modeling approach to assess the effect of short-term high PM_2.5 exposure on all-cause admissions, and prevalent cause-specific admissions among Medicare enrollees with CDBD (Parkinson's disease-PD, Alzheimer's disease-AD and other dementia). Methods: We constructed daily zipcode counts of hospital admissions of Medicare beneficiaries older than 65 across the United-States (2000–2014). We obtained daily PM_2.5 estimates from a satellite-based model. A propensity score matching approach was applied to match high-pollution (PM_2.5 > 17.4 μg/m³) to low-pollution zip code-days with similar background characteristics. Then, we estimated the percent change in admissions attributable to high pollution. We repeated the models restricting the analysis to zipcode-days with PM_2.5 below of 35 μg/m³. Results: We observed significant increases in all-cause hospital admissions (2.53% in PD and 2.49% in AD/dementia) attributable to high PM_2.5 exposure. The largest observed effect for common causes was for pneumonia and urinary tract infection. All the effects were larger in CDBD compared to the general Medicare population, and similarly strong at levels of exposure considered safe by the EPA. Conclusion: We found Medicare beneficiaries with CDBD to be at higher risk of being admitted to the hospital following acute exposure to PM_2.5 levels well below the National Ambient Air Quality Standard defined as safe by the EPA.