Air pollution ‘increases dementia risk’

Research published this week has linked exposure to high levels of air pollution with an increased risk of dementia.

The findings, published yesterday (18 September) in the scientific journal BMJ Open builds on previous research by scientists in Canada, which identified a potential link between pollution, living near a major road and an increased dementia risk (see airqualitynews.com story).

Researchers in London have drawn a link between exposure to air pollution and dementia

Researchers from King’s College London, St George’s University of London and Imperial College all took part in the research, which took into account the pollutants nitrogen dioxide (NO2) and fine particulate matter (PM 2.5).

As part of the latest study, researchers looked at data from over 130,000 people, between the ages of 50 and 79, who lived within the M25 in Greater London and who did not have a dementia diagnosis at the beginning of the study in 2005.

They followed these people for an average of 6.9 years to see if they went on to get a dementia diagnosis. They found that 1.7% of the people involved in the study were diagnosed with dementia within this follow-up period.

Assessment

Researchers calculated the levels of pollutants including nitrogen dioxide, particulates, ozone and night-time noise pollution in individual London postcodes every year from 2004 until 2010.

By collecting anonymised information about the addresses of people who received a dementia diagnosis, the researchers then compared diagnosis rates to the level of air pollution in different areas.

Their findings suggested that living in one of the areas of London with the highest levels of nitrogen dioxide pollution was associated with a 40% higher risk of dementia than living in one of the least polluted parts of the city.

The study concluded: “We have found evidence of a positive association between residential levels of air pollution across London and being diagnosed with dementia, which is unexplained by known confounding factors.”

Dr Iain Carey, Senior Lecturer in Epidemiology at St George’s, said: “While these findings need to be treated with caution, they do replicate results from other recent international studies which have suggested a link between exposure to air pollution and dementia. More research is now needed to investigate whether curbing exposure to pollution might be able to delay the progression of dementia.”

‘Importance’

Commenting on the findings, Dr David Reynolds, chief scientific officer at Alzheimer’s Research UK, said that the research underscored the need to work towards clean air in towns and cities.

He said: “The link between air pollution and dementia risk is a growing area of research. This study highlights the importance of further studies that look into exposure to pollution over a longer period of time, and investigate the possible biological mechanisms underlying this link.

“While research in this area continues, air pollution can impact a number of different aspects of our health and working towards cleaner air in our cities should be an important public health goal.”

Chris Large, senior partner at the behaviour change charity Global Action plan, organiser of the national Clean Air Day campaign said that the research provides evidence that greater public awareness of issues related to the impacts air pollution are required.

He said: “We need to radically improve public understanding of how dangerous air pollution really is. It would be great to get posters in every doctor’s surgery, but the size of the problem calls for much more – a massive and sustained public health campaign on a similar scale to that of smoking, to make sure everyone understands the extent of air pollution, and what they can do to tackle it and protect their health.

“Hardly a day passes without more evidence of the profound damage air pollution is having on the nation’s physical and mental health, especially that of the most vulnerable – surely there is enough evidence now to pull out all the stops and help everyone protect their health, starting today?”

Related Links
BMJ Open – Are noise and air pollution related to the incidence of dementia? A cohort study in London, England