Abstract
Epidemiological evidence suggests air pollution exposure may increase risk of Alzheimer’s disease and related dementias (ADRD). However, previous U.S. studies have predominantly focused on hospitalizations, which fails to fully capture ADRD. Here we constructed two national population-based cohorts of those aged 65 and above from the Medicare Chronic Conditions Warehouse (2000-2018), including doctor visits, to investigate the impact of long-term exposure to ambient fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) on dementia and AD incidence, respectively. We identified ~2.0 million incident dementia cases (N=12,233,371; dementia cohort) and ~0.8 million incident AD cases (N=12,456,447; AD cohort). Per interquartile range (IQR) increase in the 5-year average PM2.5 (3.2 µg/m3), NO2 (11.6 ppb), and warm-season O3 (5.3 ppb) over the past 5 years prior to diagnosis, the hazard ratios (HRs) were 1.060 (95% confidence interval [CI]: 1.054, 1.066), 1.019 (95% CI: 1.012, 1.026), and 0.990 (95% CI: 0.987, 0.993) for incident dementias, and 1.078 (95% CI: 1.070, 1.086), 1.031 (95% CI: 1.023, 1.039), and 0.982 (95%CI: 0.977, 0.986) for incident AD, respectively, for the three pollutants. For both outcomes there was strong evidence of linearity in concentration-response relationships for PM2.5 and NO2, suggesting the lack of a clear safe threshold for these health-harmful pollutants. Our study suggests that exposures to PM2.5 and NO2, but not O3, may increase the incidence of dementia and AD. Improving air quality may reduce the burden of ADRD and promote healthy aging.
Associations of Long-Term Air Pollution Exposure with Incident Dementia among Older U.S. Adults: The Health and Retirement Study