Living near heavy traffic may lead to dementia as you grow older. People who live within 164 feet of highway-sized or similarly trafficked roads are 7% more likely to develop dementia compared with folks living around one-fifth mile away. The cause? Pollution, in the forms of both particles and noise.
These findings come from researchers at the University of Toronto, Carleton University, Dalhousie University, Oregon State University, and Health Canada, and are part of a study that set out to establish any connections between air pollution in cities, and dementia, Parkinson’s disease, and multiple sclerosis. What they found is that concentrated traffic pollution does indeed correlate with dementia, but not with Parkinson’s or MS.
The study took data from the records of over 6.5 million Ontario residents, aged from 20-85, and used their postal codes to map their homes. The researchers then sought any correlation between the two. What they found was a significant increase in dementia in those living near heavy traffic. The theory is that neurodegeneration is caused both by particles from the pollution and also by the noise of living near a busy road.
One limitation of this study is, obviously that it only shows correlation, not causation. That is, there's no way to prove that living near busy roads is the cause of dementia. The most you can conclude is that people living close to heavy traffic also happen to develop dementia more readily. Busy roads are bad for any number of other reasons, so this can just be added to the argument of why we should get rid of them.
As more people move to live in cities—some estimates say 70% of the world's population will live in urban areas by 2050—these problems will only increase. The most desirable solution is to remove cars altogether, along with heavy goods vehicles. Failing that, zero-emissions cars reduce both pollution and noise, so at least they won't be physically damaging innocent people who just happen to live nearby.