air pollution dementia

Living Close to Major Roads or Highways Linked to Dementia

By Lecia Bushak | January 24th, 2020

Air pollution has been associated with a myriad of chronic health conditions, from asthma to cancer. It’s now believed to also increase the risk of neurological diseases like dementia and Parkinson’s, according to a new study.

The study examined 678,000 people between the ages of 45 and 84 living in Vancouver, and tracked their proximity to major roads or highways. They found that living less than 50 meters from a major road — or under 150 meters from a highway — was linked to a greater risk of developing not only dementia, but also Parkinson’s and even multiple sclerosis (MS).

The study tracked participants initially from 1994 to 1998, then followed up from 1999 to 2003. Using postal code data, the researchers identified each participant’s proximity to roads, as well as exposure to air pollution, noise and green spaces. People living near major roads or highways experienced a 14 percent increased risk of developing dementia (but not Alzheimer’s) or Parkinson’s.

Roads, Air Pollution and Dementia

Though there’s plenty of evidence supporting an association between pollution and health issues, scientists still don’t fully understand the biological mechanisms that cause damage in the body and brain. But there are a few theories.

“Pollutants can penetrate the blood-brain barrier and do damage to the brain, which is one possible reason why air pollution is linked to neurological disorders,” Lead researcher Weichan Yuchi, a PhD candidate at UBC’s School of Public Health, said in an interview with Being Patient.

“Another potential factor is when air pollutants break into the body, the pollutants will likely induce whole-body inflammation,” she continued. “Whole-body inflammation impacts multiple organs in the body, including the brain.”

Yuchi explained that the data set in her study was an older one (air pollution levels would hardly be the same now as they were decades ago), and pollution regulations have improved since then. However, air pollution continues to be an issue—and a public health concern.

Air pollution levels may be decreasing a little bit compared to one or two decades ago, but it’s still a concern,” Yuchi said.

This isn’t the first study to identify an association between pollution and dementia. A recent study found that older women who were exposed to more air pollution had a higher chance of developing structural changes in the brain, including atrophy. And another study released just this week found that heavy air pollution exposure among small children (specifically, among one-year-olds) was linked to structural brain changes as early as age 12.

Yuchi says she hopes her research will spur policymakers and urban planners to consider reducing highways and traffic in residential areas, and add more green spaces for protective benefits.

“At the population level, the take home message is that we’re hoping that the decision makers in terms of urban planning would increase accessibility to green spaces and reduce air pollution from traffic would be important for neurological health,” she said.

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