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Living close to major roads leads to higher risk of Parkinson’s and dementia: UBC study

New research analyzing more than 650,000 individuals in Vancouver found proximity to sources of air pollution can affect neurological health — but green space has protective effects

The results of a UBC study published in the peer-reviewed medical journal Environmental Health in January 2020 suggest air pollution and living close to major roads is connected to a higher risk of Parkinson’s disease and dementia.

“We wanted to understand who develops these neurologic diseases and who does not,” Dr. Michael Brauer, professor in the University of British Columbia’s School of Population and Public Health and one of the study’s authors, told The Narwhal. 

“We wanted to know, if you live close to a major road, were you more likely to develop a disease than somebody who did not live close to a major road?”

The study analyzed data for 678,000 individuals ages 45 to 84 living in Metro Vancouver between 1994 and 2003. As well as administrative health data, each individual’s proximity to a major road, exposure to air pollution, exposure to traffic noise and proximity to green space was analyzed based on their postal codes.

Why consider the population’s neurological health?

This study focused on four neurological disorders: Parkinson’s disease, multiple sclerosis (MS), Alzheimer’s disease and non-Alzheimer’s dementia. All of them are progressive diseases, meaning symptoms will gradually worsen over time.

Neurological diseases, including the four studied, are one of the leading causes of disability in Canada. None of the four disorders have a known cure and cost Canada’s health care system billions.

Brauer said that little is known about why some individuals develop these disorders and others don’t — particularly beyond aging, a known risk factor. Understanding the role the environment and urban design play could result in preventative measures being taken, and in turn, savings in health spending.

A connection to fine particulate matter

Medical data like physician codes, hospitalization data, medical billing data and prescription drug information was analyzed to determine if individuals who did not have neurological disorders between 1994 and 1998 then developed Parkinson’s disease, MS, Alzheimer’s disease or dementia in the years between 1999 and 2003.

Results showed that living less than 50 metres from a major road or less than 150 metres from a highway was associated with a 14 per cent increased risk for non-Alzheimer’s dementia and a seven per cent increased risk for Parkinson’s disease. 

Brauer notes that the number of Alzheimer’s disease and MS cases was low, meaning a relationship between road proximity, air pollution and these neurologic disorders can’t be made.

The hypothesis is that the increased risk for cognitive disorders based on road proximity has to do, at least in part, with a connection to fine particulate matter, nitrogen dioxide and nitric oxide in the air.

Lynn Canyon Park Andy Li

A tree in Vancouver’s 617-acre Lynn Canyon Park. The UBC study found proximity to green spaces has protected effects for neurological health. Photo: Andy Li

‘Green spaces protect you against its effects’

However, the results found proximity to green spaces — street trees and parks — has protective effects, even if there is still air pollution and if the individual lived near a major road.

“Even though people were [neurologically] affected by air pollution, they were less affected if where they lived was greener,” Brauer said.  

Brauer said the findings show we should be thinking about incorporating greenery and parks into residential neighbourhoods, as well as relying less on motor vehicles and separating motor vehicles from where people are spending time, to benefit Canadians’ neurological health.

However, more research still needs to be done. Next, Brauer and his team plan to expand this study beyond Metro Vancouver.

“[Analyzing] a larger population will also allow us to look at more combinations of noise, air pollution, road proximity and green space,” Brauer said. “And perhaps [we can] untangle a little bit more about what’s going on with regard to the aging population’s neurological health.” 

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