PM2.5 exposure factors in worsening dementia

New research has linked exposure to fine particulate matter (PM_2.5) to a worsening of dementia symptoms and an increase in the brain changes associated with Alzheimer’s disease (AD).

Researchers used data involving autopsy cases collected at the Center for Neurodegenerative Disease Research Brain Bank at the University of Pennsylvania in Philadelphia, Pennsylvania, US. A total of 602 patients (mean age at death 78 years, 54.5 percent male, 94.4 percent White) with common forms of dementia and/or movement disorders and older controls were included in the analysis.

The mean PM2.5 concentration was estimated over the year before death or the last dementia assessment (Clinical Dementia Rating Sum of Boxes [CDR-SB]) using a spatiotemporal prediction model at residential addresses. Outcomes included dementia severity and 10 dementia-associated neuropathologic measures.

More than half of the cases (53.2 percent) carried at least one ε4 allele of the APOE, which has been established as the strongest genetic risk factor for sporadic AD. Overall, the cases were highly educated with a median of 16 years of education and had a moderate level of dementia (median CDR-SB score of 12 at last assessment). AD (47.3 percent) was the most common clinical diagnosis, followed by Parkinson’s disease with dementia (14.1 percent).

Higher PM2.5 exposure prior to death was associated with 19-percent greater odds of more severe AD neuropathologic change (odds ratio, 1.19, 95 percent confidence interval [CI], 1.11–1.28). Similarly, in a subset of 287 patients with CDR-SB records, higher levels of PM2.5 exposure prior to CDR-SB assessment correlated with greater cognitive and functional impairment.

AD neuropathologic change mediated 63 percent of the association between higher PM2.5 exposure and greater cognitive and functional impairment.