Breathing polluted air nearly doubles the risk of dementia in older women, according to a new study published in Translational Psychiatry.
The researchers focused on the effects of breathing in the tiny particles found in air pollution. They concluded that women who are exposed to levels of particulate matter exceeding federal standards were more likely to develop dementia. Fine particulate matter comes from a range of sources, including the burning of fossil fuels.
Women are at higher risk of developing Alzheimer's, the most common form of dementia. The study used data from thousands of women across several states as well as studies on mice.
Using air samples collected near the 110 Freeway near the University of Southern California campus, Professor Caleb Finch examined the effects of air pollution on the brains of mice. When mice bred with the gene APOE-e4, which is known to increase the risk of developing Alzheimer's, were exposed to the polluted air, the effect on their brains was more significant than on those breathing air that met federal standards.
"We now know that the major Alzheimer's risk gene APOE-e4 has an environmental component," says Finch.
The study is part of a growing body of research connecting dementia and pollution. A Canadian study published last month, for example, concluded “living close to heavy traffic was associated with a higher incidence of dementia.”
Dr. Debra Cherry, vice president of Alzheimer’s Greater Los Angeles, says the study suggests “yet another way in which our environment can assault our brain.”
Cherry said that many people who live in areas prone to air pollution are also subject to other risk factors for Alzheimer’s and other dementias, including higher levels of obesity and diabetes.
Southern California has had problems with levels of particulate matter in the air for years. In 2015, air in the South Coast Air Quality Management District exceeded the daily standards for particulate matter on 25 days.
Philip Fine, deputy executive officer with the AQMD, said the region has made progress on reducing air pollution but that a combination of a large population, multiple pollution sources, the geography of the region – and, in recent years, the drought – contributes to higher levels of particulate matter in the air Angelenos breathe.
"Because of the lack of rain, we did have challenges, particularly in 2014 and 2015," Fine said. "It kind of reversed a decades-long steady trend of improvement,” but that the region is on track to meet federal standards in the coming years.