Possible dementia link to air pollution

There is a strong link between air pollution and the risk of developing dementia, researchers claim today.

A study based in London to further investigate the known association between heart disease, stroke and respiratory disease, and air pollution. They set out to examine a possible link to neurodegenerative diseases such as dementia.

Information was analysed on nearly 131,000 patients aged 50 to 79 years at the start of the study in 2004. At this point they were dementia-free. Local levels of exposure to air pollutants, specifically nitrogen dioxide (NO2), fine particulate matter (PM2.5), and ozone (O3), were estimated.

Results are published today (19 September) in BMJ Open. Over the following seven years, 1.7% pf the participants were diagnosed with dementia, including Alzheimer’s disease. This group was significantly more likely to be exposed to higher levels of NO2 and PM2.5.

Being in the top fifth of NO2 and PM2.5 exposure was linked to a 40% higher risk of being diagnosed with dementia than being in the bottom fifth, even when taking into account all other known risk factors.

The authors, led by Dr Iain Carey of St George’s, University of London, UK, explain that this study can’t establish causation – but there are several plausible pathways for air pollutants to reach the brain.

They write: "Traffic related air pollution has been linked to poorer cognitive development in young children, and continued significant exposure may produce neuroinflammation and altered brain innate immune responses in early adulthood."

They add that curbing exposure to air pollution could lead to significant public health gains.

Carey, I. M. et al. Are noise and air pollution related to the incidence of dementia? A cohort study in London, England. BMJ Open 19 September 2018; doi: 10.1136/bmjpen-2018-022404


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