New research suggests that living near a major roadway may increase your risk for developing Alzheimer’s disease and dementia. The study, published January 4th in The Lancet, demonstrates that there is a correlative relationship between proximity to major roads and development of these mental conditions, though the relationship is not obviously causal.
The increased risk was most pronounced among people who lived within 160 feet of a major roadway. The closer people lived to heavily-trafficked roads, the higher the risk.
According to Hong Chen, the study’s author, “Our study suggests that busy roads could be a source of environmental stressors that could give rise to the onset of dementia.”
Paul Wright, a neurologist who reviewed the study, said, “This large study brings to light a major health concern that needs to be considered.”
“With dementia rates on the rise and a significant public health concern, society needs to be aware of the ramifications of this study. Urban planners and policymakers need to also consider the impact of urban development on the health of its population.”
The research collected data on 6.6 million people living in Ontario, from 2001 to 2012. The subjects ranged in age from 20 to 85. Postal codes were used to measure how distant each subject was from highly-trafficked streets.
They cross-referenced the subjects’ proximity to traffic with their medical records to try to demonstrate relationships with medical conditions, especially neurological conditions such as Parkinson’s, MS and dementia.
During the study window, over 243,000 subjects developed dementia, 31,500 developed Parkinson’s and 9,250 developed multiple sclerosis. Of these conditions, only dementia was found to have a statistically significant correlation with living proximity to traffic.
The people living within 164 feet of a major roadway suffered a 7% increase in dementia risk. Over 300 feet, the risk increase drops to 4%. At 650 feet, it’s 2%. Beyond that, there is no demonstrable increase in risk.
By the researchers’ estimates, if there is, indeed, a causal relationship between traffic exposure and dementia, about 11% of dementia cases are probably a result of living too close to a main road.
The risk increase is likely a consequence of increased exposure to pollutants like nitrogen dioxide and fine particulates, among other compounds. They even believe that long-term exposure to traffic noise might have something to do with it.
According to Chen, “With widespread exposure to traffic and growing rates of dementia, even a modest effect from near-road exposure could pose a large public health burden. More research to understand this link is needed.”