Living near a major road may increase dementia risk

Posted on 4th January 2017

The Lancet: Living near major roads and the incidence of dementia, Parkinson’s disease, and multiple sclerosis: a population-based cohort study

A study by researchers in Canada has found that those who live near a major road may also have a higher risk of dementia. The research is published on 4 January in the journal The Lancet.

Currently in the UK there are 850,000 people living with dementia. This study is the first to extend findings from previous research in the US and Germany that suggested pollution from traffic on major roads could be linked to neurodegenerative diseases. The study identified a link between living near a major road and an increased dementia risk, which was found to be independent of other known risk factors for dementia such as smoking, obesity and lack of exercise.

To investigate the link between changes in pollution levels associated with living near a major traffic road and increased risk of neurodegenerative disease, the researchers studied 6.6 million people. The team looked at the people’s postcode areas to identify how close they lived to surrounding major roads.  Then the scientists studied the medical records of the participants from 2001 to 2012, to identify if any of the residents had gone on to develop a neurodegenerative disease.

Over the decade long study 243,000 people went on to develop dementia. The researchers observed that nearly all of the people in the study, 95%, lived within one kilometre of a major road such as a motorway or A road, with half of the people living less than 200 meters away from a major road. The scientists found people who lived within 50 meters of a major road had a 7% higher risk of developing dementia, compared to people who lived more than 200 meters away who had no increase in their risk. The study however did not discover any link to living near a major road and the development of either multiple sclerosis or Parkinson’s disease.  The researchers estimate that nearly one in ten cases of dementia could possibly be linked to living near a major road. With those residents living closer to a major road showing a stronger risk of developing dementia.

Dr David Reynolds, Chief Scientific Officer at Alzheimer’s Research UK, said:

“There are 850,000 people in the UK living with dementia, and therefore interest in the risk factors driving the condition is high. This research is interesting in its identification of an association between dementia and major roads, but if any causal link exists between these two factors, it can’t be confirmed by this study.”

“Conditions like dementia have multiple risk factors including age and genetics, and other social factors relating to where people live in cities could also be playing a part here. This study has identified major roads and air pollutants from traffic as possible risk factors for dementia, a finding which will need further investigation before any firm conclusions can be drawn about the relative risks of air pollutants for dementia versus other risks such as smoking, lack of exercise or being overweight.”

“Studies like this are valuable in revealing new factors that could be implicated in Alzheimer’s disease and other dementias, and opening new avenues for further research. Alzheimer’s Research UK is funding research focusing on reducing the risk factors surrounding dementia, and is dedicated to finding a way of preventing or slowing down the progression of this devastating condition.”

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