Living Close to Major Roads Increases Parkinson’s Risk, According to Canadian Study

People who live less than 50 meters (about 54 yards) from major roads or 150 meters (164 yards) from a highway have a higher risk of developing Parkinson’s disease or other neurodegenerative disorders, according to a Canadian study.

Meanwhile, green spaces such as parks seem to offer protection and lower the risk of developing diseases of the brain, the study found, so the findings should be considered when planning new neighborhoods.

The study, “Road proximity, air pollution, noise, green space and neurologic disease incidence: a population-based cohort study,” was published in Environmental Health.

The number of cases of Parkinson’s and other neurological conditions are on the rise. This trend is forecast to continue as the population ages since the diseases occur later in life.

It is known that smoking and lack of exercise increase the risk of developing neurological conditions like Parkinson’s or Alzheimer’s disease, but it is difficult to pinpoint other modifiable risk factors. Some studies, however, suggest that environmental exposures such as traffic proximity and air pollution might also be to blame.

Traffic pollution and the resulting poor air quality certainly is harmful for lungs and the respiratory system, so it’s not surprising that it could damage  other parts of the body. Several studies from around the world have shown that living close to a road is associated with poorer brain function. However, it is always difficult to draw conclusions because so many different factors need to be taken into consideration — for example age, diet or lifestyle.

Now, University of British Columbia researchers gathered health data of approximately 678,000 residents (ages 45–84) of Metro Vancouver, Canada, a rapidly growing urban area comprising 21 municipalities.

Using postal code data, researchers measured individual exposures to road proximity, air pollution, noise levels and greenness. The team defined greenness as the distance to a park or open space, which they estimated using satellite images of the region.

Air pollution data was gathered by estimating exposure to small particles in the air, black carbon or soot and nitrogen dioxide from car exhausts. Changes in address, neighborhood income, ethnicity and education levels were taken into account, as well as preexisting illnesses known to increase the risk of neurological conditions.

“This analysis was the first large population-based study to investigate the onset of four major neurological disorders in association with road proximity and air pollution as well as joint effects of noise and greenness,” the researchers wrote.

Exposure data was collected from 1994 to 1998 and the participants were monitored from 1999 and 2003 for diagnosis of Parkinson’s, Alzheimer’s, multiple sclerosis (MS) and non-Alzheimer’s dementia. Altough the researchers noted that the measured exposure period was too short, since it takes more than four years for neurodegenerative diseases to develop, data from before 1994 was not available.

During the monitoring period there were 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 multiple sclerosis.

Living in an area with higher levels of air pollution was shown to increase the risk of Parkinson’s and non-Alzheimer’s dementia, but not Alzheimer’s or MS.

Additionally, living close to a major road (less than 50 meters) or highway (less than 150 meters) was associated with a 7% increase in the risk of developing Parkinson’s and a 14% increase in the risk of developing non-Alzheimer’s dementia. It also was positively correlated with the risk of developing Alzheimer’s and MS.

Both road proximity and air pollution seemed to have greater effects on the incidence of non-Alzheimer’s dementia and Parkinson’s among those younger than 65. Noise levels did not seem to affect the risk of any of these diseases.

“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 [multiple sclerosis] at the population level,” study lead author Weiran Yuchi, from the University of British Columbia, said in a press release.

Greenness seemed to protect against the development of non-Alzheimer’s dementia, Parkinson’s and Alzheimer’s.

“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. There may even be benefits from just the visual aspects of vegetation,” said Michael Brauer, PhD, professor at the University of British Columbia and senior author of the study.

The study highlights the importance of taking green spaces into account in future studies to ensure unbiased results, and also because they seem to be beneficial for a healthy community. “More research is needed, but our findings do suggest that urban planning efforts to increase accessibility to green spaces and to reduce motor vehicle traffic would be beneficial for neurological health,” Yuchi said.