Dementia is more common in people who live within 50 metres of a major road than those who live further away, according to a study looking at 6.6 million people.
The study, published in The Lancet today (Thursday 5 January 2016), found no link between traffic exposure and Parkinson's disease or multiple sclerosis.
The observational study estimated that up to one in 10 (7-11 per cent) cases of dementia among those who live within 50 metres of a major road could be attributable to traffic exposure.
The researchers tracked all adults aged between 20 and 85 living in Ontario, Canada – approximately 6.6 million people – for over a decade from 2001 to 2012. They used postcodes to determine how close people lived to a road and analysed medical records to see if they went on to develop dementia, Parkinson's disease or multiple sclerosis.
Almost all people (95 per cent) in the study lived within one kilometre of a major road and half lived within 200 metres of one. Over the study period, more than 243000 people developed dementia, 31500 people developed Parkinson's disease and 9250 people developed multiple sclerosis.
Dr Doug Brown, Director of Research at Alzheimer's Society said:
'This study offers some evidence that people who live near major roads in Ontario, Canada have a slightly increased risk of dementia. Although this was a thorough study in a large number of people, the research hasn’t yet shown what causes this link, so we can’t be sure that reducing pollution or noise from traffic would decrease the risk of dementia.
'The causes of dementia are complex. Lifestyle factors such as exercise, eating healthily and avoiding smoking will reduce our chances of developing dementia. Age remains the strongest known risk factor for dementia, but emerging evidence on aspects of the environment could become important to help prevent dementia in future.'