Feb. 3 (UPI) -- Reducing air pollution levels can help slow declines in brain function in women, a study published Thursday by PLOS Medicine found.
Women who lived in regions of the United States that saw improvements in air quality performed better on measures of brain function and memory over a 20-year period than those living in areas with stable air quality, the data showed.
Although performance on these assessments of cognitive function continued to decline as the women in the study aged, those living in areas that experienced reductions in air pollution appeared to have a slower progression of dementia symptoms, the researchers said.
"Scientists have known that improved air quality extends life expectancy in the elderly, saves lives in adults, promotes lung growth and reduce the risk of asthma in kids," among other benefits, study co-author Diana Younan told UPI in an email.
"In this study, we found women living in locations with greater improvement in air quality tended to have a slower decline in cognitive function," Younan, an observational research manager at drug-maker Amgen, based in Los Angeles.
This slower decline "was equivalent to being about 1 1/2 years younger," she added.
Cleaner air is already known to improve heart and respiratory health and reduce a person's risk for early death, research suggests.
An earlier study by Younan and her colleagues found that lower air pollution can reduce the risk for dementia, or decline in brain function, particularly memory, among women living in regions impacted by these improvements.
For this study, Younan and her colleagues analyzed the effects of air pollution reduction in 2,232 women who were free of dementia when the research began.
The women were annually assessed for memory and brain function over a 20-year period, the researchers said.
The researchers estimated local changes in air quality in the areas in which the study participants lived and used statistical tests to see if a reduction in air pollution was associated with slower cognitive decline, they said.
Women living in areas with greater improvements in air quality, as measured by lower amounts of particulate matter and nitrogen dioxide, tended to have a slower decline, based on scores on the two cognitive tests used in the study, the data showed.
PM2.5 is a mixture of microscopic solid substances and liquid droplets found in the air, including dust, dirt, soot and smoke, according to the Environmental Protection Agency.
Nitrogen dioxide is found in exhaust from motor vehicles, as well as emissions from the combustion of coal, oil or natural gas and various industrial sources, the agency says.
"The magnitude of slower cognitive decline that were associated with reducing the levels of these two pollutants in the air is approximately the same," Younan said.
"This suggests the potential health benefits seen in our study were a result of decreasing levels of outdoor air pollution across the U.S.," she said.