A new study suggests that air pollution may accelerate brain aging and contribute to the progression of dementia, and women with a specific gene variant are at greater risk than others.

The analysis included 3,647 women ages 65 to 79. From 1995 to 2010, researchers tracked the women’s mental ability with well-validated questionnaires and used public data from the Environmental Protection Agency to calculate air pollution levels. The study is in Translational Psychiatry.

Women who lived in areas with high concentrations of the fine particulate matter that easily penetrates the lungs, known as PM 2.5, had a 68 percent to 91 percent greater risk for cognitive decline and all-cause dementia than those with the lowest exposure.

But among the women in the study with the highest exposure and two copies of the ApoE4 gene variant, there was a 295 percent increased risk. About 2 percent of the population has two copies of the ApoE4 variant, which by itself is known to increase the risk for Alzheimer’s disease.