A recent study has discovered that people living by busy roads possess a high chance of having dementia.
Dementia is an overall term that describes a wide range of symptoms associated with a decline in memory or other thinking skills severe enough to reduce a person’s ability to perform everyday activities.
The study, which was published in The Lancet, estimates that one in 10 cases of Alzhemer’s among those living by busy roads is linked to air and noise pollution.
Each person’s medical records were examined to see who went on to develop dementia, Parkinson’s disease or multiple sclerosis.
Over the study period, more than 243,000 people developed dementia, 31,500 people developed Parkinson’s disease and 9,250 people developed multiple sclerosis.
The scientists found no link between living near a road and Parkinson’s disease or multiple sclerosis, but dementia was slightly more common in people living close to busy roads and the risk dropped off gradually in less built-up areas.
Those living within 50 metres of a busy road had a 7% higher risk in developing dementia, the risk was 4% higher risk at 50-100 metres, 2% higher risk at 101-200 metres and there was no increase in risk in those living more than 200 metres away.
Those who lived in a major city, within 50 metres of a major road and who did not move house for the duration of the study had the highest risk at 12%.
“Increasing population growth and urbanisation has 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,” said Hong Chen, the scientist who led the work at Public Health, Ontario, Canada.
Scientists have previously linked air pollution and traffic noise to reduced density of white matter (the brain’s connective tissue) and lower cognition.
Another study suggested that magnetic nano-particles from air pollution can make their way into brain tissue.
The study, which tracked roughly 6.6 million people for more than a decade, could not determine whether pollution is directly harmful to the brain.
The increased dementia risk could also be an effect of respiratory and cardiac problems caused by traffic fumes or due to other unhealthy lifestyle factors associated with living in built-up urban environments.
Rob Howard, a professor of old age psychiatry at University College London, who was not involved in the study, said: “We know that major road air pollution is bad for general health and this latest study doesn’t tell us whether the small increase in dementia risk is driven by indirect effects or whether proximity to traffic directly influences dementia pathology. Regardless of the route of causation, this study presents one more important reason why we must clean up the air in our cities.”
The study tracked all adults aged between 20 and 85 living in Ontario, Canada from 2001 to 2012, using postcodes to determine a person’s proximity to major roads.
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