Higher exposure to particulate matter may be associated with an increased risk of dementia

Higher exposure to particulate matter may be associated with an increased risk of dementia

Higher exposure to a specific type of traffic-related air pollution called particulate matter may be associated with an increased risk of dementia, according to a meta-analysis published October 26, 2022 in the online edition of Neurology®, the medical journal American Academy of Neurology. The researchers specifically looked at particulate matter, PM2.5, which consists of airborne pollutant particles less than 2.5 micrometers in diameter. All available studies on air pollution and dementia risk were included in the meta-analysis.

As people live longer, conditions such as dementia are becoming more common, so recognizing and understanding preventable risk factors is key to reducing the rise of this disease. Since a World Health Organization report showed that more than 90% of the world's population lives in areas with higher levels of air pollution than recommended, our findings provide further evidence for enforcing air quality regulations and accelerating the transition from fossil fuels to sustainable energy.”

Ehsan Abolhasani, MD, MSc, study author, Western University in London, Canada

For the meta-analysis, the researchers reviewed 17 studies. The participants were over 40 years old. All studies included more than 91 million people. Of these, 5.5 million people or 6% developed dementia.

The studies adjusted for several factors that influence a person's risk of dementia, including age, gender, smoking and education.

Researchers compared exposure to air pollution in people with and without dementia and found that people who did not develop dementia had lower average daily exposure to particulate air pollutants than people with dementia. The US Environmental Pollution Agency (EPA) considers average annual levels of up to 12 µg/m3 to be harmless.

The researchers found that the risk of dementia increased by 3% for each microgram per cubic meter (µg/m3) of increased particulate matter exposure.

"Although our meta-analysis does not prove that air pollution causes dementia, but only shows an association, we hope that these results will empower people to take an active role in reducing their exposure to air pollution," Abolhasani said. “By understanding the risk of dementia from air pollution, people can take steps to reduce their exposure, such as using sustainable energy, choosing to live in areas with lower air pollution, and advocating for lower traffic pollution in residential areas.”

They also examined nitrogen oxides, which form smog, nitrogen dioxide and ozone pollution, but found no significantly increased risk when these other classes of pollutants were considered alone.

A limitation of the meta-analysis was the small number of available studies on this specific topic. Abolhasani said further studies are needed.

Source:

American Academy of Neurology

Reference:

Abolhasani, E., et al. (2022) Air pollution and incidence of dementia: A systematic review and meta-analysis. Neurology. doi.org/10.1212/WNL.0000000000201419.

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