Living next to traffic ups dementia?

Study found no link between traffic exposure and Parkinson's disease or multiple sclerosis.

New Delhi: Dementia is more common in people living within 50 metres of a major road than those who live further away, according to a study looking at 6.6 million people published in The Lancet.

According to the first of its kind study, one in 10 (seven per cent to 11 per cent) cases of dementia among those who live within 50 metres of a major road could be attributable to traffic exposure.

Experts said that this was the first study to investigate the link between living close to heavy traffic and the onset of major neurogenerative disease. Importantly, previous studies had suggested that air pollution and traffic noise may contribute to neurodegeneration, with one study even finding that living near a road was associated with reduced white matter and lower cognition.

During their study, 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.

Using the postcodes to determine how close people lived, the experts analysed medical records to see if they went on to develop dementia, Parkinson’s disease or multiple sclerosis. Significantly, the study found no link between traffic exposure and Parkinson’s disease or multiple sclerosis.

Alarmingly, 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.

“While there was no association between living near a road and Parkinson’s disease or multiple sclerosis, dementia was more common the closer people lived to busy roads,” it said.

As per the experts, the risk of developing dementia reduced as people lived further away from a main road – with a 7% higher risk in developing dementia among those living within 50 metres, a 4% higher risk at 50-100 metres, a 2% higher risk at 101-200 metres and no increase in risk in those living more than 200 metres away.

The researchers also found that long-term exposure to two common pollutants (nitrogen dioxide and fine particulate matter) was associated with dementia but this did not account for the full effect, meaning other factors are also likely to be involved. These could include other air pollutants or noise from traffic.

Lead author Dr Hong Chen, Public Health Ontario, Canada said,“Our study suggests that busy roads could be a source of environmental stressors that could give rise to the onset of dementia. 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. More research to understand this link is needed, particularly into the effects of different aspects of traffic, such as air pollutants and noise.”

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