Living close to major roads increases dementia risk
medwireNews: Living close to major roads is associated with an increased risk for dementia, but not for Parkinson’s disease or multiple sclerosis, study findings reported in The Lancet show.
The results indicate that up to one in 10 cases of dementia among patients living within 50 meters of a major road is attributable to traffic exposure.
“This study suggests that improvements in environmental health policies and land use planning aimed at reducing traffic exposure can have considerable potential for prevention of dementia, which would lead to a broad public health implication,” comment researcher Hong Chen (Public Health Ontario, Toronto, Canada) and colleagues.
The researchers monitored new cases of dementia, Parkinson’s disease, and multiple sclerosis among approximately 6.6 million adults aged 20–85 years living in Ontario between 2001 and 2012 and used their postal-code address in 1996 as a measure of their proximity to major roadways.
Almost all the participants lived within 1000 m of a major road and half lived within 200 m. Over the course of the study, there were 243,611 incidences of dementia, 31,577 of Parkinson’s disease, and 9247 of multiple sclerosis.
The risk for developing dementia decreased with distance from major roads. People living within 50 m of a major road had a 7% greater risk for dementia than those living more than 300 m away. This compared with a 4% greater risk for people living within 50–100 m of a major road and a 2% greater risk for those living within 101–200 m. There was no increased risk for individuals living more than 200 m away.
The researchers note that urban residents, especially those living in major urban centers and those who never moved, were particularly at risk. For these individuals, living within 50 versus more than 300 m of a major road increased the risk for dementia by between 9% and 12%.
By contrast, there were no associations between proximity to major roads and the risk of Parkinson’s disease or multiple sclerosis.
The associations between dementia risk and close proximity to major roads were robust to various sensitivity analyses for factors such as education, smoking, obesity, and physical activity.
But there was modest attenuation when fine particulate matter and nitrogen oxide levels were accounted for. Both of these were positively associated with dementia but they did not fully explain the effect of major road proximity on dementia risk, which the researchers say suggests other pollutants or factors such as noise may be involved.
They acknowledge that the effect of traffic exposure on brain health is not fully understood, but believe that “systemic inflammation arising from traffic-related air pollution is probably important.”
In a related editorial, Lilian Calderón-Garcidueñas (The University of Montana, Missoula, USA) and Rodolfo Villarreal-Ríos (Historian and Economist, Mexico City) say the findings may go beyond the issue of improving air quality, and “also provide new insights into the mechanisms for the early development of oxidative stress, neuroinflammation and neurodegeneration, and opportunities to prevent and ameliorate such harmful brain effects starting in childhood and the teen years.”
They say: “We must implement preventive measures now, rather than take reactive actions decades from now.”
By Lucy Piper
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