People who live near roads with heavy traffic face a higher risk of developing dementia than those living further away, possibly because pollutants get into their brains via the bloodstream, researchers in Canada said Thursday.
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A study in The Lancet medical journal found that people who lived within 55 yards of high-traffic roads had a 7 percent higher chance of developing dementia compared to those who lived more than 328 yards away from busy roadways.
"Air pollutants can get into the bloodstream and lead to inflammation, which is linked with cardiovascular disease and possibly other conditions such as diabetes,” said Ray Copes, an environmental and occupational health expert at Public Health Ontario who conducted the study with colleagues from Canada's Institute for Clinical Evaluative Sciences.
“This study suggests air pollutants that can get into the brain via the bloodstream can lead to neurological problems," Copes continued. Dementia is caused by brain diseases, most commonly Alzheimer's disease, which results in the loss of brain cells and affects memory, thinking, behavior, navigational and spatial abilities and the ability to perform everyday activities.
Independent experts said the Canadian study had important implications for public health around the world. Tom Dening of the Center for Old Age and Dementia at the U.K.'s Nottingham University said the findings were "interesting and provocative."
"It is unlikely that Ontario has the worst air quality in the world, so the risks might be even greater in cities that are habitually wrapped in smog," he said.
The research team analyzed records of more than 6.5 million Ontario residents aged 20 to 85 and found 243,611 cases of dementia between 2001 and 2012. Then they mapped residents' proximity to major roadways using postal codes.
The increase in the risk of developing dementia went down to 4.0 percent if people lived 55 to 109 yards from major traffic, and to 2.0 percent if they lived within 110 to 217 yards. At more than 217 yards, the elevated risk faded away.
The scientists said their results could be used to help town and city planners take traffic conditions and air pollution into account as urban areas become more densely populated.
The World Health Organization estimated the number of people with dementia in 2015 at 47.5 million, and that total is rising rapidly as life expectancy increases and societies age.