"The study shows the unexpectedly adverse effects of air pollutants on brain function in the elderly," Caleb Finch, the ARCO/William F. Kieschnick Professor in the Neurobiology of Aging at the University of Southern California at Davis, said in a statement.
Jennifer Ailshire -- a sociologist, demographer and postdoctoral student at the USC Davis School of Gerontology -- said the study involved about 15,000 men and women age 50 and older, whose cognitive tests were matched with maps of air pollution.
After accounting for several factors -- including age, race/ethnicity, education, smoking and respiratory and heart conditions -- the study found the more the air pollution, the lower the tests scores.
Brains aged at a rate of three years more quickly among those who lived in areas with the worst pollution than those who lived in areas with the least pollution.
"I hope this research draws more attention to the adverse effects of air pollution on population health and particularly the health of older adults," Ailshire said. "This issue is especially relevant for the Los Angeles area, where pollution levels are so high, far above national levels and U.S. Environmental Protection Agency standards, and the population of older adults is growing so rapidly."
The findings were presented at the 65th annual meeting of the Gerontological Society of America in San Diego.