FRIDAY, Nov. 20, 2020 (HealthDay News) — Late-life exposure to particulate matter with aerodynamic diameter <2.5 µm (PM2.5) is associated with Alzheimer disease (AD) pattern similarity (AD-PS) scores among women, corresponding to an increase in AD risk, according to a study published online Nov. 18 in Neurology.

Diana Younan, Ph.D., from the University of Southern California in Los Angeles, and colleagues examined whether late-life exposure to PM2.5 contributes to progressive brain atrophy predictive of AD. Participants were older women with up to two brain magnetic resonance imaging (MRI) scans performed in 2005 to 2006 and in 2010 to 2011. AD-PS scores were used to capture high-dimensional gray matter atrophy in brain areas vulnerable to AD. A spatiotemporal model was implemented to estimate three-year average exposure to PM2.5 preceding MRI-1.

The researchers found that in cross-sectional analyses, for 1,365 women aged 77.9 ± 3.7 years in 2005 to 2006, no association was seen between PM2.5 and baseline AD-PS score. Longitudinally, there was an association noted for each interquartile range increase of PM2.5 with elevated AD-PS scores during follow-up, equivalent to a significant increase in AD risk over five years (hazard ratio, 1.24). The association persisted after adjustment for multiple confounding variables and was observed with PM2.5 levels below U.S. regulatory standards.

“Not only did we find brain shrinkage in women exposed to higher levels of air pollution, we also found it in women exposed to air pollution levels lower than those the EPA [U.S. Environmental Protection Agency] considers safe,” the authors write.

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