MORE than 10m Britons are at a higher risk of dementia because they live near a busy road, scientists have concluded.
Those living in big cities are up to 12% more likely to develop dementia as a result of traffic fumes, according to a study of more than 6m people. The risk rises the closer people live to heavy traffic.
The scientists said their findings were “of real public health significance” and the results would increase pressure for tougher curbs on pollution.
More than 200,000 people a year develop dementia in Britain. One in 10 cases in people living near busy city streets could be explained by pollution, according to researchers, who called for homes to be built further from traffic.
Although the Canadian study cannot prove that pollution causes dementia, Ray Copes of Public Health Ontario, one of its authors, said: “This is the most powerful study design that one could practically come up with to investigate this link . . . This adds another reason why we should be reducing levels of traffic-related air pollution.”
His team used a database of all adults in Ontario to track where 2.2m older people had lived since 1996, of whom 244,000 developed dementia. Those living 100-200 metres from a main road were 2% more likely to get dementia; the figure rose to 4% for people 50-100 metres away and 7% for those within 50 metres, according to the study in The Lancet.
“Even a 7% increase is of real public health significance”
People in big cities were 12% more likely to get dementia if they lived within 50 metres of a busy road, after the figures were adjusted for class, weight, smoking and other risks.
Half the population of Ontario lives within 200 metres of a busy road and 20% within 50 metres. Copes said the figures were likely to be higher in Britain.
“The evidence from experimental work suggests that ultra-fine particles from engines do get taken up through the lungs, circulate in the body and produce inflammation,” he said. “That has been implicated in a variety of diseases and it now appears we have evidence that would suggest a similar link for dementia.”
Diesel vehicles have come in for particular criticism over high levels of nitrogen dioxide emissions, one of the key pollutants implicated by Copes’s team. “Diesels are a real concern and there’s a real need to look at emissions standards for these vehicles,” he said.
The stress of living with constant noise may also play a role, he added. While the risk for any individual was relatively small, Copes said: “We are dealing with a very common condition, so even a 7% increase is of real public health significance.”
Tom Dening, director of the centre for dementia at Nottingham University, said: “It is certainly plausible that air pollution from motor exhaust fumes may contribute to brain pathology that over time may increase the risk of dementia, and this evidence will add to the unease of people who live in areas of high traffic concentration.”
Air pollution has also been shown to increase the risk of lung cancer, heart disease and asthma and is blamed for 40,000 deaths in Britain each year.
Chris Smyth, Health Editor
This article first appeared in The Times