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Reducing air pollution lowers dementia risk, study finds

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Improving air quality appears to slow cognitive decline and reduce the risk of developing dementia in older women, according to a new study by researchers from the Keck School of Medicine of USC in California.

Previous studies have shown that exposure to air pollution later in life is connected to a higher risk of developing dementia, but until now it has been unknown how improving air quality would impact brain health.

The researchers analysed the link between reductions in air pollution and the development of dementia among women aged 74 to 92 using third-party data.

The women, who did not have dementia at the beginning of the study, were given annual cognitive function tests from 2008 to 2018 to determine whether they developed dementia. Using participants’ home addresses, the study group created mathematical models to estimate air pollution levels at these locations over time.

Among women living in locations with the greatest reductions in two types of air pollutants — fine particulate matter (PM2.5) and the traffic-related pollutant nitrogen dioxide (NO2) — the risk of dementia decreased by 14 per cent and 26 per cent respectively. The benefit from lower air pollution was consistent despite differences among study participants in age, geographic area, socioeconomic background, cardiovascular risk factors and Apolipoprotein E genotype.

“Our study is important because it is one of the first to show that reducing air pollution over time may benefit the brain health of older women by decreasing their likelihood of developing dementia,” said Xinhui Wang, PhD, lead author of the study. “The takeaway message is that reducing air pollution exposure can promote healthier brain aging.

“Our results shows that the benefits may be universal in older women, even those already at greater risk for dementia”.

Improvements in air quality were also associated with benefits to overall cognitive function and memory, suggesting a positive impact on multiple underlying brain regions.

Dementia, which disproportionately affects women, is not only devastating for patients and their families – it is also among the most expensive chronic diseases in the US and other countries. According to research conducted by the RAND Corporation, the economic cost of dementia was between $159bn (£117bn) and $215bn (£158bn) in 2010 and the figure is expected to double by 2040.

“Alzheimer’s disease and related dementias (ADRD) are immensely costly both to the healthcare system and to the families who struggle to take care of their older members,” said Diana Younan, PhD, the study’s other lead author.

“Our research suggests that tightening the air quality standards may help to prevent Alzheimer’s disease and related dementias in older women and, in turn, reduce its societal burden.”

The research paper - 'Association of improved air quality with lower dementia risk in older women' - has been published in the journal Proceedings of the National Academy of Sciences.

A similar study was conducted in Sweden over a period of 11 years, with the final research results published in March 2020. One of the key conclusions was that people suffering from a heart condition and living in areas with even minimal air pollution are at increased risk of dementia.

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