In a new study, researchers found that older women who live in locations with higher levels of air pollution may have more brain shrinkage, the kind seen in Alzheimer’s disease, than women who live in locations with lower levels.
They looked at fine particle pollution and found that breathing in high levels of this kind of air pollution was linked to shrinkage in the areas of the brain vulnerable to Alzheimer’s disease.
The research was conducted by a team at the University of Southern California.
Fine particle pollution consists of microscopic particles of chemicals, smoke, dust, and other pollutants suspended in the air.
They are no larger than 2.5 micrometers, 30 times smaller than the width of a human hair.
Smaller brain volume is a known risk factor for dementia and Alzheimer’s disease, but whether air pollution alters brain structure is still being researched.
The study involved 712 women with an average age of 78 who did not have dementia at the start of the research.
All women received MRI brain scans at the start of the study and five years later.
Researchers used the residential addresses of each participant to determine their average exposures to air pollution in the three years before the first MRI scan.
They then divided participants into four equal groups. The lowest group was exposed to an average of 7 to 10 micrograms of fine particle pollution per cubic meter of air (μg/m3).
The highest group was exposed to an average of 13 to 19 μg/m3. The U.S. Environmental Pollution Agency (EPA) considers average yearly exposures up to 12 μg/m3 to be safe.
Researchers measured signs of Alzheimer’s disease in the brain, an AI tool that had been trained to identify patterns of brain shrinkage specific to an increased risk of Alzheimer’s disease by reading the brain scans of people with the disease.
The team found for each 3 μg/m3 increase in air pollution exposure levels, there was a greater extent of brain shrinkage over five years, which was equivalent to a 24% increased risk of Alzheimer’s disease.
The findings have important public health implications, because not only did the researchers find brain shrinkage in women exposed to higher levels of air pollution, they also found it in women exposed to air pollution levels lower than those the EPA considers safe.
The team says while more research is needed, federal efforts to tighten air pollution exposure standards in the future may help reduce the risk of Alzheimer’s disease in older people.
One author of the study is Diana Younan, Ph.D.
The study is published in Neurology.
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