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21 September 2018

Does air pollution cause dementia?

Will Richard, Communications & Engagement Officer

According to a new study air pollution appears to be linked to an increased risk of developing dementia.

photo of London looking up the Thames river at sunset - red sky

According to a new study co-authored by Professor Frank Kelly, School of Population Health & Environmental Sciences, air pollution appears to be linked to an increased risk of developing dementia.

Air pollution is now an established risk factor for heart disease, stroke and respiratory disease but its potential role in neurodegenerative diseases, such as dementia, isn’t clear. To better understand this Professor Kelly and colleagues used carefully calculated estimates of air pollution levels across Greater London to assess potential links with new dementia diagnoses.

The team analysed data from just under 131,000 patients aged 50 to 79 in 2004 who had, at the time, not been diagnosed with dementia. Based on their residential postcodes, researchers estimated their yearly exposure to specific air pollutants: nitrogen dioxide (NO2), fine particulate matter (PM2.5), and ozone (O3). The health of patients was then tracked for an average of seven years until a diagnosis of dementia, death, or deregistration from the practice, whichever came first.

Their results, published in the journal BMJ Open, showed that during the monitoring period, 2181 patients (1.7%) were diagnosed with dementia, including Alzheimer’s disease. These diagnoses were associated with ambient levels of NO2 and PM2.5 pollution at patients’ homes. Those living in the most polluted areas were 40 per cent more likely to be diagnosed with dementia than those living in the least.

Professor Frank Kelly, Professor of Environmental Health and Director of King’s Environmental Research Group, said of the results:

We hypothesise that it is reactions by our body’s immune system to elevated pollution occurring over and over again that leads to the eventual tissue damage such as to the lungs, blood vessels or brain. Even if the impact of air pollution were relatively modest, the public health gains would be significant if it emerged that curbing exposure to it might delay progression of dementia. Our calculations suggest that it elevates risk by 7%, so [that would suggest] approximately 60,000 of the total 850,000 dementia cases in the UK, in mathematical terms.

Professor Frank Kelly