LONDON • People living near major roads have a higher chance of developing dementia, according to a large-scale study published in British medical journal The Lancet yesterday.
The research looked at records of more than 6.5 million adults living in Ontario, Canada, between 2001 and 2012, and found that those living less than 50m from a busy road had a 7 per cent higher incidence of dementia than those living more than 200m away.
The risk was 4 per cent above normal for those living 50m to 100m from main roads and 2 per cent higher among those 100m to 200m away.
There was no discernible elevated risk among people living more than 200m from a major route.
The study, led by Dr Hong Chen from Public Health Ontario, found that long-term exposure to two common pollutants - nitrogen dioxide (NO2) and fine particulates - were associated with dementia, but did not account for the full effect.
This suggests that other factors - such as noise or other pollutants - may play a contributing role.
Key findings of the study
The following are the key findings of a study linking dementia to living near major roads:
•People living within 50m of high-traffic roads have a 7 per cent higher chance of developing dementia than those living more than 200m away.
• The increase in the risk of dementia went down to 4 per cent if people lived 50m to 100m away.
• The heightened risk diminished to 2 per cent at a distance of 101m to 200m from a busy road.
•At more than 200m, there was no elevated risk of dementia.
•There was no correlation between major traffic proximity and Parkinson's disease or multiple sclerosis.
Dr Chen's team analysed 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 research did not establish any link between proximity to heavy traffic and other neurological conditions such as Parkinson's disease or multiple sclerosis.
According to the World Health Organisation, 47.5 million people worldwide have dementia - a syndrome marked by deterioration in memory, thinking, behaviour and the ability to perform everyday activities.
Some 7.7 million new cases of dementia are reported every year, with Alzheimer's disease being the most common cause and contributing to 60 per cent to 70 per cent of cases. Other causes of dementia include stroke and hypertension.
Pollution has long been suspected as playing a role in the development of Alzheimer's, but no clear link has been established until now.
"Our study suggests that busy roads could be a source of environmental stressors that could give rise to the onset of dementia," Dr Hong said.
"Increasing population growth and urbanisation has placed many people close to heavy traffic and, with widespread exposure to traffic and growing rates of dementia, even a modest effect from near-road exposure could pose a large public health burden."
Dementia affects an estimated one in 10 people aged over 60 in Singapore.
AGENCE FRANCE-PRESSE, REUTERS