Air pollution and dementia using longitudinal electronic health record data from the Indian Health Service

Abstract

AbstractBackgroundAir pollution has been identified as an important risk factor for dementia in previous studies. As a unique population with a history of colonization, American Indians have long been disproportionately affected by air pollution. However, few studies have investigated the effects of air pollution on the risk of developing dementia in American Indians. This study aims to address this important knowledge gap.MethodCounty‐level average air pollution data in 2003‐2007 were downloaded from the land‐use regression models developed by the Center for Air, Climate, & Energy Solutions (CACES) and merged with data from the Indian Health Service (IHS) National Data Warehouse and related electronic health record databases between fiscal year (FY) 2007‐2013. We assigned air pollution exposure to IHS users based on their county of residence and calculated 5‐year averages of PM2.5, O3, CO, and NO2 in each county. A total of 14,910 American Indians who were 65+ years old in FY2007, used IHS services at least once each year, and were dementia free between FY2007‐2009 were included in the main analysis. Cox proportional hazard models with age as the time scale were employed to examine the association of air pollution with dementia incidence, adjusting for potential confounders.ResultThe PM2.5 levels in the IHS counties were lower than those in all US counties during 2003‐2013, while the levels of other air pollutants were similar to the US (Figure 1). More dementia incident cases were found in IHS counties with higher O3 levels (Figure 2). In multivariable Cox regression models (Table1), we found a significant positive association between dementia and O3 with a hazard ratio (HR) of 1.26 (95% CI: 1.02‐1.55) per 1 ppb standardized O3, while the associations between dementia and PM2.5, and CO were not statistically significant. We found similar results in sensitivity analyses using longer lags between air pollution and dementia or replacing CO by NO2 in the regression model.ConclusionOur study suggests that exposure to O3 is associated with the higher risk of dementia in American Indians. Future efforts to reduce exposure to air pollution might help lower dementia risk in American Indian communities.