Living near a highway may increase dementia risk by 7 per cent

Health

Living near a highway may increase dementia risk by 7 per cent

4 January 2017

A congested road — Don’t breathe it in
Dominic Lipinski/Getty

Living close to a motorway or highway may increase the risk of developing dementia, according to a study of more than six million adults in Canada.

Tracking these people over a period of 11 years found a clear link between dementia incidence and living near a main road, comparable to the M1 or M4 in the UK, or major state or interstate highways in the US. Compared with those whose homes were more than 300 metres away from a busy road, people living within 50 metres of heavy traffic had a 7 per cent higher risk of developing dementia.

This increase falls to 4 per cent in people living between 50 to 100 metres of a busy road, and 2 per cent in people living between 101 and 200 metres. At greater distances, there was no evidence of a link with the condition.

“Our findings show the closer you live to roads with heavy day-to-day traffic, the greater the risk of developing dementia,” says , at Public Health Ontario, who 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.”

In the air

The study also found that long-term exposure to nitrogen dioxide and fine particulates – two common components of air pollution – is associated with dementia, but that other factors are likely to be involved too. Other studies have also linked air pollution to dementia risk.

However, the study was not able to determine whether roads and air pollution themselves help cause dementia. It’s possible that something else that is associated with these factors may instead be to blame.

“This study has identified major roads and air pollutants from traffic as possible risk factors for dementia, a finding which will need further investigation before any firm conclusions can be drawn about the relative risks of air pollutants for dementia versus other risks such as smoking, lack of exercise, or being overweight,” says , at the charity Alzheimer’s Research UK.