"This is the first study to really show, in a statistical model, that air pollution was associated with changes in people's brains and that those changes were then connected with declines in memory performance," said study resarcher Andrew Petkus, Assistant Professor University of South California in US.
Previous research has suggested that fine particle pollution exposure increases the risk for Alzheimer's disease and related dementias.
What scientists haven't known is whether PM2.5 alters brain structure and accelerates memory decline.
For the study, published in the journal Brain, researchers used data from 998 women, aged 73 to 87, who had up to two brain scans five years apart as part of the landmark Women's Health Initiative launched in 1993 by the US National Institutes of Health and enrolled more than 160,000 women to address questions about heart disease, cancer and osteoporosis.
Those brain scans were scored on the basis of their similarity to Alzheimer's disease patterns by a machine learning tool that had been "trained" via brain scans of people with Alzheimer's disease.
The researchers also gathered information about where the 998 women lived, as well as environmental data from those locations to estimate their exposure to fine particle pollution.
When all that information was combined, researchers could see the association between higher pollution exposure, brain changes and memory problems even after adjusting to take into account differences in income, education, race, geographic region, cigarette smoking and other factors.
"This study provides another piece of the Alzheimer's disease puzzle by identifying some of the brain changes linking air pollution and memory decline. Each research study gets us one step closer to solving the Alzheimer's disease epidemic," Petkus said.
"Our hope is that by better understanding the underlying brain changes caused by air pollution, researchers will be able to develop interventions to help people with or at risk for cognitive decline," Petkus added.
( With inputs from IANS )