Exposure to air pollution late in life raises the risk of developing dementia. But does that mean improving air quality can reduce those risks?

A new study in the journal PNAS suggests the answer is yes.

“These findings are important because they're strengthening the evidence that high levels of air pollution can harm the brain, and that reducing your exposure may promote healthier brain aging in older women,” said co-author Diana Younan, formerly of the University of Southern California.

Researchers used 20 years of data from the Women's Health Initiative Memory Study — Epidemiology of Cognitive Health Outcomes to study more than 2,200 women ages 74-92.

"We focused on studying older woman because of women are disproportionately affected by Alzheimer's disease," said Younan.

They found a 10% improvement in current U.S. Environmental Protection Agency fine particulate standards translated to a 14% reduction in dementia risk.

Lowering nitrogen dioxide levels brought a 26% risk reduction. 

"These differences were similar to what we might have observed in women if they were two to three years younger," said Younan.

The pattern held true regardless of age, education, geographic region or cardiovascular history.