Scientists Say Improving Air Quality Can Cut Dementia Risk In Older People

Researchers at Alzheimer's Association -- a Chicago-based non-profit organisation -- have shared three studies that show the ill effects of pollution and its link with dementia-causing Alzheimer's, warning the governments to put regulations in place to curb air pollution to reduce the rates of people suffering from this condition.

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The three studies were reported at the Alzheimer's Association International Conference (AAIC) 2021 that was conducted in Denver. They looked at the effect of reducing nitrogen dioxide and PM 2.5 on cases of Alzheimer's in a particular population.

First Study

The first study on this list was conducted by Xinhui Wang, assistant professor of research neurology at the University of Southern California and his team. They tested the hypothesis that if older women who resided in locations with a greater reduction in air pollution could result in a slower decline in their cognitive function and would have fewer chances of developing dementia.

For the study, they looked at a group of women from the age group of 74 to 92 from the WHIMS-ECHO study that was funded by the National Institutes of Health. These women didn¡¯t have dementia at the beginning.

These participants were observed between 2008 and 2018, with cognitive function tests performed every year to understand if the test subjects are showing signs of dementia development.

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Researchers also got the addresses of participants to see an estimated pollution level at their homes over time. The researchers discovered that in the decade-long period, air quality improved greatly.

During a median of 6 years, some level of cognitive decline was evident due to the subjects ageing. However, for every 1.2 micrograms per cubic metre reduction in PM2.5, there was a 14 percent reduced risk of getting dementia and for every 5.3 parts per billion reductions in NO2, there was a 26 percent reduced risk of dementia.

Second Study

A similar study was conducted by the University of California, San Diego researchers, but with a large sample of 7,000 participants aged 65 years and older. They discovered that a 15 percent reduced risk of all-cause dementia and a 17 percent reduced risk of Alzheimer's disease for every decrease in PM2.5 levels. This decrease was regardless of the socio-demographic and health behaviour factors and the APOE genotype -- a genetic risk factor for dementia.

Third Study

To the uninitiated, Alzheimer's is known to be caused by the abnormal build-up of proteins in and around brain cells. One of the proteins involved is called beta-amyloid plaques. The other protein dubbed tau is responsible for the tangles within brain cells.

Accumulation of beta-amyloid plaques is one of the most prominent indicators of Alzheimer's disease, and researchers were looking for a link between this plaque buildup and air pollution.

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For this, a study by researchers from the Department of Epidemiology at the University of Washington looked at links between exposure to PM2.5, PM10, NO2 and A¦Â1-40 -- a major protein component of plaques in over 3,000 individuals who were originally dementia-free.

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The study also looked at pollution levels at the address of the participant for time periods up to 20 years prior to taking blood tests for the study.

Individuals who have been a part of the study for a long time -- up to eight years -- showed a strong association between all three pollutants and A¦Â1-40, thus marking the first human data suggesting air pollution could be an important factor in the development of dementia.

Claire Sexton, director of scientific programs & outreach at the Alzheimer¡¯s Association said in a statement, ¡°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. 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.¡±