A national cohort study (2000–2018) of long-term air pollution exposure and incident dementia in older adults in the United States

Abstract

Air pollution may increase risk of Alzheimer’s disease and related dementias (ADRD) in the U.S., but the extent of this relationship is unclear. Here, we constructed two national U.S. population-based cohorts of those aged ≥65 from the Medicare Chronic Conditions Warehouse (2000–2018), combined with high-resolution air pollution datasets, to investigate the association of long-term exposure to ambient fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) with 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, concentration-response relationships for PM2.5 and NO2 were approximately linear. Our study suggests that exposures to PM2.5 and NO2 are associated with incidence of dementia and AD.

Long-term effects of PM2.5 components on incident dementia in the northeastern United States

“…Other authors have also used a “clean” period while studying dementia or Alzheimer’s disease. 30 , 56 These requirements would increase the possibility that the individual did not have dementia prior to Medicare enrollment. Subjects were entered into the cohort on the first day of the year following the period of “clean” claims, and they were followed until the first diagnosis or death of an outcome of interest across all claims in Medicare or the end of follow up.…”

“…We used annual average PM 2.5 mass and components during the same year window because we had observed previously that PM 2.5 in the current year could have higher estimate effects on dementia than alternative exposure windows, implying an acceleration of an existing dementia progression by PM 2.5 . 30 …”

“… 29 Existing studies have often relied on inpatient hospitalization records as a measure of incidence. A recent study by Shi et al., 30 based on nationwide Medicare data in the United States including doctor visits, also provides evidence that long-term exposure to PM 2.5 may increase the incidence of dementia.…”

“…To fill these knowledge gaps, we build on the study by Shi et al. 30 by conducting a population-based cohort study of the Medicare dataset and a well-validated high-resolution (1 km × 1 km) PM 2.5 components dataset from 2000–2017. The latter includes data on OM, NO 3 − , SO 4 2− , BC, SOILs, and SS in the northeastern United States, where better exposure estimates exist.…”

TUBE Project: Transport-Derived Ultrafines and the Brain Effects

“…Neurological diseases and exacerbated cognitive dysfunction have already been shown to be associated with air pollution [ 8 , 9 , 10 , 11 , 12 ] and, in particular, living in the vicinity of roads with high traffic density [ 13 , 14 ]. Furthermore, air pollution is linked with Alzheimer’s disease (AD) [ 14 , 15 ], the most common neurodegenerative disease and the main cause of dementia in the elderly.…”