A comparison of PM 2.5 exposure estimates from different estimation methods and their associations with cognitive testing and brain MRI outcomes.

Background: Reported associations between particulate matter with aerodynamic diameter ≤2.5 μm (PM _2.5 ) and cognitive outcomes remain mixed. Differences in exposure estimation method may contribute to this heterogeneity.
Objectives: To assess agreement between PM _2.5 exposure concentrations across 11 exposure estimation methods and to compare resulting associations between PM _2.5 and cognitive or MRI outcomes.
Methods: We used Visit 5 (2011-2013) cognitive testing and brain MRI data from the Atherosclerosis Risk in Communities (ARIC) Study. We derived address-linked average 2000-2007 PM _2.5 exposure concentrations in areas immediately surrounding the four ARIC recruitment sites (Forsyth County, NC; Jackson, MS; suburbs of Minneapolis, MN; Washington County, MD) using 11 estimation methods. We assessed agreement between method-specific PM _2.5 concentrations using descriptive statistics and plots, overall and by site. We used adjusted linear regression to estimate associations of method-specific PM _2.5 exposure estimates with cognitive scores (n = 4678) and MRI outcomes (n = 1518) stratified by study site and combined site-specific estimates using meta-analyses to derive overall estimates. We explored the potential impact of unmeasured confounding by spatially patterned factors.
Results: Exposure estimates from most methods had high agreement across sites, but low agreement within sites. Within-site exposure variation was limited for some methods. Consistently null findings for the PM _2.5 -cognitive outcome associations regardless of method precluded empirical conclusions about the potential impact of method on study findings in contexts where positive associations are observed. Not accounting for study site led to consistent, adverse associations, regardless of exposure estimation method, suggesting the potential for substantial bias due to residual confounding by spatially patterned factors.
Discussion: PM _2.5 estimation methods agreed across sites but not within sites. Choice of estimation method may impact findings when participants are concentrated in small geographic areas. Understanding unmeasured confounding by factors that are spatially patterned may be particularly important in studies of air pollution and cognitive or brain health.
Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Melinda Power reports financial support was provided by National Institutes of Health.Melinda Power reports a relationship with National Institutes of Health that includes: funding grants. Melinda Power reports a relationship with U.S. Department of Defense that includes: funding grants. Melinda Power reports a relationship with DC DEPARTMENT OF HEALTH that includes: funding grants. Melinda Power reports a relationship with Biogen that includes: consulting or advisory. Erin Bennett reports a relationship with Massachusetts General Hospital that includes: consulting or advisory. Eun Sug Park reports a relationship with National Institutes of Health that includes: funding grants. Jeff D. Yanosky reports a relationship with National Institutes of Health that includes: funding grants. Duanping Liao reports a relationship with National Institutes of Health that includes: funding grants. Joel D. Kaufman reports a relationship with National Institutes of Health that includes: funding grants. Joel D. Kaufman reports a relationship with U.S. Environmental Protection Agency that includes: funding grants. Lianne Sheppard reports a relationship with National Institutes of Health that includes: funding grants. Lianne Sheppard reports a relationship with Health Effects Institute that includes: funding grants. Adam Szpiro reports a relationship with National Institutes of Health that includes: funding grants. Adam Szpiro reports a relationship with Health Effects Institute that includes: funding grants. Adam Szpiro reports a relationship with Health Effects Institute that includes: consulting or advisory. Eric Whitsel reports a relationship with National Institutes of Health that includes: funding grants. Eric Whitsel reports a relationship with USFederal Aviation Administration that includes: funding grants.If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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