A new study involving women aged 74 to 92 years shows that residing in locations with a greater reduction in air pollution levels in late life had associations with a slower decline in cognitive function.
Cognitive agingTrusted Source refers to a decline in cognitive function that typically occurs with aging. Previous studies examining the association between higher air pollution levels and cognitive decline have yielded mixed results.
The results of this study add to data suggesting an adverse impact of outdoor air pollution on cognitive aging.
The study’s lead author, Dr. Diana Younan, former Senior Research Associate at USC Keck School of Medicine, Los Angeles, told Medical News Today, “We found women living in locations with greater improvement in air quality tended to have a slower decline in cognitive function, which was equivalent to being about 1 or 1.5 years younger.”
Air quality improvements
The adverse effects of air pollution on human health are well-recognized. Studies have shown that lower air pollutant levels have links to a longer lifespan and a decline in the prevalence of respiratory illnesses.
Previous research had shown that exposure to air pollution had associations with an increased risk of dementia. However, data showing a correlation between higher pollution levels and cognitive decline that normally occurs with aging have been inconsistent.
The Environmental Protection Agency (EPA) established the National Ambient Air Quality Standards in 1970 to safeguard human health. These standards have placed a cap on the permissible levels of six air pollutants.
The subsequent adoption of policies to restrict air pollution has resulted in a gradual decline in air pollution levels over the past 50 years in the United States.
“Scientists have known that improved air quality extends life expectancy in the elderly, saves lives in adults, promotes lung growth, reduces the risk of asthma in kids, and increases the birth weights in newborns. In this study, we asked a big question: do the public health benefits resulting from improving air quality in the U.S. help older Americans maintain their brain health?” Dr. Younan noted.
Estimating air pollution levels
The present study consisted of 2,232 women aged 74–92 years enrolled in the Women’s Health Initiative Memory Study-Epidemiology of Cognitive Health Outcomes study between 2008 and 2012.
The study comprised a geographically diverse group of participants residing in the 48 contiguous U.S. The team did not include individuals with dementia at the time of enrollment in the research.
The researchers administered telephone-based annual assessments to the participants to measure general cognitive function. Besides the battery of tests to assess general cognitive function, the participants also received a test to assess episodic memory specifically. Episodic memory is the ability to recall personal experiences and past events, and deficits in this faculty are one of the early signsTrusted Source of Alzheimer’s disease.
The researchers then estimated improvements in air quality for each participant over the 10-year period before their study enrollment. According to the residential address of the participants during this timeframe, the researchers estimated the participant’s annual exposure to air pollution with the help of models and EPA monitoring data.
Specifically, the team estimated the participant’s exposure to nitrogen dioxide and fine particulate matter or PM2.5, which comprises air pollutants with a diameter of 2.5 micrometers and smaller.
The team estimated air quality improvements by calculating the difference between the 3-year average air pollution exposure immediately before enrollment and 10 years before the onset of their participation.