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Cutting air pollution levels ‘improves brain function and lowers risk of dementia’, studies suggest

Reducing levels of air pollution may improve cognitive function and reduce the risk of dementia, according to a series of reports released by the US Alzheimer’s Association.

Though previous research has established links between exposure to long-term air pollution and Alzheimer’s disease – the most common cause of dementia – the new research is the first broad body of evidence showing that reducing pollution, especially fine particulate matter (PM2.5) in the air and pollutants from the burning of fossil fuels, is associated with lower risk of all-cause dementia and Alzheimer’s disease.

Worsening air quality around the world due to urbanisation and industrialisation in recent decades means the increasing cases of dementia have become an international health crisis, according to scientists attending the Alzheimer’s Association International Conference 2021 in Denver.

Among the key findings are that a reduction of PM2.5 concentration over 10 years was associated with a reduced risk of all-cause dementia in French individuals by 15 per cent and of Alzheimer’s disease by 17 per cent for every microgram less of gaseous pollutant per cubic meter of air.

Also, long-term exposure to air pollutants was associated with higher blood levels of beta amyloid levels – the amino acids which cause the plaques found in the brains of Alzheimer’s sufferers.

This suggests a possible biological connection between air quality and the physical brain changes which define Alzheimer’s disease, the researchers said.

“We’ve known for some time that air pollution is bad for our brains and overall health, including a connection to amyloid buildup in the brain,” said Claire Sexton, the Alzheimer’s Association director of scientific programs and outreach.

“But what’s exciting is we’re now seeing data showing that improving air quality may actually reduce the risk of dementia. These data demonstrate the importance of policies and action by federal and local governments, and businesses, that address reducing air pollutants.”

In one of the studies, Dr Xinhui Wang, assistant professor of research neurology at the University of Southern California, led research investigating whether older women living in locations with greater reductions in air pollution may have slower decline in their cognitive function and be less likely to develop dementia

The researchers found that, in general, air quality greatly improved over the 10 years before the study began. During a median of six years of follow-up, cognitive functions tended to decline as women aged, as expected. However, for those living in locations with greater reduction of PM2.5 and NO2, their risk of dementia decreased by 14 per cent and 26 per cent. This was similar to the lower level of risk seen in women two to three years younger.

These benefits were seen regardless of age, level of education, the geographic region where they lived and whether they had cardiovascular disease, the researchers said.

“Our findings are important because they strengthen the evidence that high levels of outdoor air pollution in later life harm our brains, and also provide new evidence that by improving air quality we may be able to significantly reduce risk of cognitive decline and dementia,” Dr Wang said.

“The possible benefits found in our studies extended across a variety of cognitive abilities, suggesting a positive impact on multiple underlying brain regions.”

The research is published by the Alzheimer’s Association.

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