By Stephen Beech
Air pollution may directly contribute to dementia, warns new research.
People with greater exposure to fumes and other airborne pollutants are at greater risk of developing Alzheimer’s disease, according to the study.
Alzheimer’s is the most common form of dementia, affecting more than 50 million people worldwide.
Exposure to air pollution is a known risk factor for Alzheimer’s, and for several other common chronic health conditions including high blood pressure, stroke and depression.
Those chronic conditions are also linked to Alzheimer’s disease.
But, until now, it was unclear whether air pollution causes those chronic conditions, which then lead to dementia, or if the conditions might amplify the effects of air pollution on brain health.
American researchers studied more than 27.8 million U.S. Medicare recipients aged 65 or older from 2000 to 2018.
They looked at individuals’ air pollution exposure level and whether they developed Alzheimer’s disease, while emphasising the role of other chronic conditions.
The findings, published in the journal PLOS Medicine, showed that greater exposure to air pollution was associated with an increased risk of Alzheimer’s disease, and that association was slightly stronger in people who had suffered a stroke.
However, high blood pressure and depression had little additional impact.
Study lead author Dr. Yanling Deng said: “Overall, the findings suggest that air pollution contributes to Alzheimer’s disease mostly through direct pathways rather than through other chronic health conditions.
“However, people with a history of stroke may be especially susceptible to the harmful effects of air pollution on brain health.”
The study indicates that improving air quality could be an important way to prevent dementia and protect older adults.
Dr. Deng, of Emory University in Atlanta, Georgia, said: “We found that long-term exposure to fine particulate air pollution was associated with a higher risk of Alzheimer’s disease, largely through direct effects on the brain rather than through common chronic conditions such as hypertension, stroke, or depression.”
She added: “Our findings suggest that individuals with a history of stroke may be particularly vulnerable to the harmful effects of air pollution on brain health, highlighting an important intersection between environmental and vascular risk factors.”
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