Living near highways linked to higher dementia risk

Researchers have revealed that living near major roads or highways is linked to higher incidence of dementia, Parkinson's disease, Alzheimer's disease and multiple sclerosis (MS).

For the findings, published in the journal Environmental Health, researchers from the University of British Columbia analysed data for 678,000 adults in Metro Vancouver.

They found that living less than 50 metres from a major road or less than 150 metres from a highway is associated with a higher risk of developing neurological disorders -- likely due to increased exposure to air pollution.

"For the first time, we have confirmed a link between air pollution and traffic proximity with a higher risk of dementia, Parkinson's, Alzheimer's and MS at the population level," said study lead author Weiran Yuchi from the University of British Columbia in Canada.

Neurological disorders, a term that describes a range of disorders, are increasingly recognised as one of the leading causes of death and disability worldwide.

Little is known about the risk factors associated with neurological disorders, the majority of which are incurable and typically worsen over time.

For the study, researchers analysed data for 678,000 adults between the ages of 45 and 84 who lived in Metro Vancouver from 1994 to 1998 and during a follow-up period from 1999 to 2003.

They estimated individual exposures to road proximity, air pollution, noise and greenness at each person's residence using postal code data.

During the follow-up period, the researchers identified 13,170 cases of non-Alzheimer's dementia, 4,201 cases of Parkinson's disease, 1,277 cases of Alzheimer's disease and 658 cases of MS.

For non-Alzheimer's dementia and Parkinson's disease specifically, living near major roads or a highway was associated with 14 per cent and seven per cent increased risk of both conditions, respectively.

When the researchers accounted for green space, they found the effect of air pollution on the neurological disorders was mitigated.

The researchers suggest that this protective effect could be due to several factors.

"For people who are exposed to a higher level of green space, they are more likely to be physically active and may also have more social interactions," said study senior author Michael Brauer.

"There may even be benefits from just the visual aspects of vegetation," Brauer added.