Could Living Near a Highway Increase Your Risk of Dementia?

There are a number of reasons why it could be hazardous to live near a highway—noise and traffic ranking pretty high—but according to a new Canadian study in The Lancet, your risk of developing dementia could increase the closer you live to a major road.

In a study of more than 6 million people, researchers found a link between dementia development and a person's proximity to a major road, such as an interstate highway or parkway. People living less than 50 meters (164 feet) from a major road were 7 percent more likely to develop dementia than people who live more than 300 meters from one. The risk drops as you get further away, with a 4 percent higher chance at 50 to 100 meters away and a 2 percent higher chance at a distance of 101 to 200 meters. The study was conducted on people living in Ontario between 20 and 85 years old from 2001 to 2012.

“Our findings show the closer you live to roads with heavy day-to-day traffic, the greater the risk of developing dementia,” says Public Health Ontario epidemiologist Hong Chen, who co-led the study. “With our widespread exposure to traffic and the greater tendency for people to live in cities these days, this has serious public health implications.”

While the study found a link between highway proximity and risk of dementia, there's no concrete evidence as to why this actually happens. However, there have been studies done on the link between developing dementia and air pollution, which is an everyday hazard when living near a busy highway. As the study points out, though, the risk shrinks significantly as you move further away.

"There is a gradient of increased risk as you get closer to major roadways," study co-lead Ray Copes, chief of environmental and occupational health at Public Health Ontario, told CNN. "By the time you're 200 meters away, the risk is essentially down to baseline."

According to the World Health Organization, there are 47.5 million people living with dementia worldwide, with 7.7 million new cases diagnosed every year—the most common cause being Alzheimer's disease, which accounts for 60 to 70 percent of cases. The team also investigated whether there was any higher risk of developing Parkinson's disease or multiple sclerosis when living near a highway but found no link.

[h/t New Scientist]