New evidence review uncovers ‘significant’ link between particulate matter and dementia

A review of evidence by researchers in Canada has uncovered a ‘significant’ association between exposure to particulate matter – a type of air pollution – and the development of dementia.

Particulate matter is a mixture of solid particles and liquid droplets from the burning of fossil fuels and nitrogen oxide also produced from road traffic exhaust.

Due to the small size of many of the particles that form particulate matter, some of these toxins may enter the bloodstream and be transported around the body, lodging in the heart, brain and other organs. Therefore, exposure can result in serious impacts to health, especially in vulnerable groups of people such as the young, elderly and those with respiratory problems.

In the research, published in the journal Neurology, the team reviewed information collected from 17 existing studies assessing the link between dementia and air pollution. Together, the total included population was 91 million, with 5.5 million being diagnosed with dementia.

The researchers compared rates of air pollution exposure for people both with and without dementia, finding that people who did not develop dementia had a lower average daily exposure to fine particulate matter air pollutants than people who did.

Specifically, they found that the risk of dementia increased by 3% for every 1µg/m3 increase of fine particulate matter exposure.

The team also looked at nitrogen oxides, nitrogen dioxide and ozone exposure, but found a ‘non-significant’ association in dementia risk when these other classes of pollutants were considered alone.

The review follows a recent UK government report by the Committee on the Medical Effects of Air Pollutants, published in July, which found a link between air pollutants and an acceleration of the decline in cognitive function and the risk of developing dementia.

"Alzheimer’s Research UK believes that the current UK government needs to do more to address this,” said Dr Sara Imarisio, head of research at Alzheimer’s Research UK.

“Its proposed air quality targets lack the ambition to reduce particulate matter pollution as quickly as possible. That’s why we’re calling for the government to implement both safe and achievable targets, in line with World Health Organization guidelines, of 10µg/m3 PM2.5 by 2030."

Imarisio also outlined that there are “several biological explanations” that could be behind the link between air pollution and dementia, and that more research is needed to understand this.