Pollution can raise risk of dementia by 40pc

Research on subjects who live within the area of the M25 shows a link to neurodegenerative disease

Living in a highly polluted area may increase the risk of dementia by as much as 40 per cent, a new study suggests. London-based research published in BMJ Open found a link between the neurodegenerative condition and exposure to nitrogen dioxide and microscopic particles known as PM2.5. The study focused on 131,000 patients aged between 50 and 79, who had not been diagnosed with dementia, registered at 75 GPS within the M25.

LIVING in a highly polluted area may increase the risk of dementia by as much as 40 per cent, a new study suggests.

London-based research, published in the journal BMJ Open, found an association between the neurodegenerative condition and exposure to nitrogen dioxide and microscopic particles known as PM2.5.

The study focused on 131,000 patients aged between 50 and 79 in 2004, who had not been diagnosed with dementia, registered at 75 general practices within the M25 area.

Those living in areas with the top fifth of nitrogen dioxide levels had a 40 per cent increased risk of being diagnosed with dementia compared with those living in areas with the lowest, the study found. A similar increase was seen with levels of PM2.5, they added.

The associations could not be explained by factors known to influence the development of the condition, but the links were more consistent for Alzheimer’s than vascular dementia.

“Our results suggest both regional and urban background pollutants may be as important as near-traffic pollutants,” wrote the scientists from the University of London, Imperial College and King’s College London.

“While toxicants from air pollution have several plausible pathways to reach the brain, how and when they may influence neurodegeneration remains speculative.” Last year, a study published in The Lancet medical journal suggested living close to a busy road increases the risk of Alzheimer’s and other forms of dementia.

Separate research, presented at the European Respiratory Society International Congress, found children who have green spaces near their homes have fewer respiratory problems such as asthma later in life.

A Defra spokesman said: “Air pollution is the top environmental risk to human health in the UK … we have put in place a £3.5bn plan to reduce harmful emissions from road transport and have launched an ambitious clean air strategy which has been commended by the World Health Organisation.”

Dr David Reynolds, chief scientific officer at Alzheimer’s Research UK, warned the latest study does not show cause and effect.

He said: “While the researchers tried to account for factors like wealth, heart disease and other potential explanations for differences in dementia rates across the capital, it is difficult to rule out other explanations for the findings.

“The diseases that cause dementia can begin in the brain up to 20 years before symptoms start to show. We don’t know where people in this study lived in the two decades before their dementia diagnosis, so we have to be cautious about how we interpret these results.”