People exposed to high levels of traffic-related air pollution are more likely to have more amyloid plaques in their brain, a condition associated with Alzheimer’s disease, a new study finds.

Seniors were nearly twice as likely to have more amyloid plaques if, in the year before their death, they lived in places with high concentrations of particle pollution caused by traffic, results show.

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Those with higher exposure in the three years before death were 87% more likely to have higher levels of plaques, the researchers added.

“These results add to the evidence that fine particulate matter from traffic-related air pollution affects the amount of amyloid plaque in the brain,” said researcher Anke Huels, an assistant professor of epidemiology with Emory University in Atlanta. However, the findings did not prove that air pollution actually causes Alzheimer's, only that there is an association.

For the study, researchers examined the brain tissue of 224 people who donated their brains at death to contribute to dementia research. The people died at an average age of 76.

The research team measured the levels of amyloid plaques and tau tangles in the people’s brains, which are two major signs of Alzheimer’s.

They then looked at the amount of air pollution at the home addresses of the patients, all of whom lived in or near Atlanta.

Higher exposures to air pollution were strongly linked to more amyloid plaques, researchers discovered.

Further, the association was independent of the presence of the main gene variant associated with a higher risk of Alzheimer’s disease, APOE e4.

Those without this gene variant displayed the strongest relationship between air pollution and signs of Alzheimer’s, researchers reported.

The new study was published Feb. 21 in the journal Neurology.

“This suggests that environmental factors such as air pollution could be a contributing factor to Alzheimer’s in patients in which the disease cannot be explained by genetics,” Huels said in a journal news release. “More research is needed to investigate the mechanisms behind this link.”