An 11 year study of 2 million people in Canada has revealed a connection between living near a major road and dementia risk
With 50 million people worldwide now suffering from dementia, a figure which is set to sharply rise over the coming decades, scientists have been scrambling to better understand the condition. A recent study published in the Lancet journal sought to examine the effect of proximity to busy roads on dementia risk, as previous links have suggested pollution may increase risk.
What was the study?
Examining 2 million people between 2001 to 2012 in the province of Ontario, Canada, the researchers compared individuals living in greater and lesser proximity to major roads. 243,611 people were diagnosed with dementia during the study's duration.
The study discovered that in comparison to those living over 300 metres away from such a road, risk was:
7% higher within 50m
4% higher between 50-100m
2% higher between 101-200m
Overall analysis suggested that around 7-11% of cases within 50 metres were correlated.
But what about other factors?
Of course, a point that springs to mind is whether proximity to a road was instead a better marker of poverty and associated lifestyle factors. However, the researchers accounted for poverty, obesity, education and smoking in their analysis; adjusting the conclusions accordingly.
"Increasing population growth and urbanisation have placed many people close to heavy traffic, and 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, particularly into the effects of different aspects of traffic, such as air pollutants and noise"
In some ways the research perhaps isn't a surprise, given that the WHO has already tied 3 million deaths each year to air pollution. Pollution has also been connected to stroke risk, heart disease, respiratory disorders and lung cancer. Pollutants like nitrogen oxides and tyre particles, and even constant noise exposure may play a role in poorer health outcomes. However, while the study suggests a relatively small link, it's not yet established. The research found a connection between road proximity and dementia rates, but did not delve into why that was the case. It does provides extra motivation to improve air quality in congested areas, but such a task is extremely difficult to undertake.
"The effects are small, but with a disorder with a high population prevalence, such effects can have important public health implications"
Ultimately of course, developing ways to prevent and reverse the condition would be far more valuable than quibbling over comparatively small risk factors. For now however, uncovering any link could help us unravel exactly what causes dementia to occur.
Read more at BBC News