Environmental Factor – August 2021: Better Air Quality May Reduce Risk of Dementia in Older Women

Improving air quality may slow cognitive decline and reduce the risk of dementia in older women in the United States, according to NIEHS-funded research. The results were presented on July 26 at the Alzheimer Association International Conference 2021.

Exposure to air pollution at the end of life is a modifiable risk factor for dementia. Better air quality is associated with decreased mortality and improved respiratory health. But until now, it was not clear whether improving air quality could improve or preserve cognitive abilities.

“Our research focuses on how environmental factors such as exposure to ambient air pollution affect brain aging, including cognitive decline and the risk of Alzheimer’s disease and associated dementia,” a Wang said. (Photo courtesy of Xinhui Wang)

“Our studies are new because they are the first to investigate the benefits of improved air quality on brain aging,” said Xinhui Wang, Ph.D., assistant research professor in neurology at the Keck School of Medicine at the University of Southern California. “The take-home message is that reducing exposure to air pollution can promote healthier brain aging.”

Link air pollution to aging brain

Wang teamed up with NIEHS beneficiary Jiu-Chiuan Chen, MD, Sc.D., associate professor of population and public health sciences at the Keck School of Medicine. Their study included 2,232 women living in the community in the United States, aged 74 to 92, who did not have dementia at the time of enrollment. The women were participating in the Women’s Health Initiative Memory Study – Epidemiology of Cognitive Health Outcomes (WHIMS-ECHO).

Researchers conducted annual telephone interviews between 2008 and 2018 to assess general cognitive status and word memory. They also used models to estimate annual exposure to inhalable fine particles with a diameter typically less than or equal to 2.5 micrometers from 1996 to 2012, as well as exposure to nitrogen dioxide in residential areas.

Better air quality, slower decline

Air quality has improved in terms of fine particles and nitrogen dioxide in the 10 years prior to listing. As expected, general cognitive state and memory decreased with age over a mean follow-up of 6.2 years. But greater improvement in air quality was associated with slower decline, regardless of age, geographic region, education, or cardiovascular factors. Based on the results, the researchers plan to study the neural processes that underlie the benefits of improved air quality on aging brain.

“Our results demonstrate the importance of federal and local government policies and regulatory actions to reduce air pollution levels more systematically,” Wang said. “The impact will be great because everyone will benefit. At the individual level, we would advocate reducing exposure by avoiding or minimizing the time spent in heavily polluted areas. Wearing an appropriate respirator may be a choice if exposure is unavoidable.

(Janelle Weaver, Ph.D., is a contract writer for the NIEHS Office of Communications and Public Liaison.)