A major study suggests Millions of people have a greater risk of developing dementia because they live near a busy road. Scientists have found people exposed to traffic fumes and noise were up to 12 per cent more likely to develop the disease. And among these people those at the highest risk are those living within 50 metres of a major road in which up to one in nine cases of dementia might be caused by traffic exposure. 
An estimated number of 850,000 people in the UK currently have dementia, and the number is expected to increase to one million by 2025! The disease is thought to be largely linked to genetics but the increasing evidence suggests that other factors such as smoking, obesity and lack of exercise may also increase the risk of dementia. 
The Canadian research reveals the closer someone lives to a major road and the longer they live there the higher their risk of developing dementia. The team chose 6.6million addresses of adults aged between 20 and 85 living in the Canadian province of Ontario, and then tracked them for 11 years between 2001 + 2012. The team found that the people living within the radius of 50m of a major road were 7 % more likely to develop dementia than those who lived 300m away. 
Britain has a population density of five times that of Ontario; many more people live near main roads, including the vast majority of people living in cities. The UK is also notoriously bad at controlling air pollution, with 37 cities across Britain persistently breaching legal limits of air toxins that are set by the EU. The new findings add to evidence that long-term exposure to air pollution and traffic noise could contribute to brain shrinkage and mental impairment. 
Scientists think this is because nitrogen dioxide and the sooty particles generated by diesel engines interfere with the blood-brain, the crucial membrane which stops harmful chemicals entering brain cells.  
They also think pollution may aggravate inflammation in the brain, a problem which can also trigger dementia. Medical experts are increasingly aware of the impact of traffic on the human health, including the risk of asthma and heart disease, but this is the first time such a strong link has been made between traffic exposure and dementia. 
British experts described the findings as ‘important’ and ‘provocative’, but stressed that they highlighted associations and did not demonstrate a causal link between exposure to traffic and dementia.  
Dr David Reynolds, chief scientific officer at Alzheimer’s Research UK, said: ‘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.’ 
Professor Tom Dening, director of the Centre for Old Age and Dementia at the University of Nottingham, said: ‘It is certainly logical that air pollution from motor exhaust fumes may add to brain pathology and that over time may increase the risk of dementia, and this evidence will add to the unease of people who live in areas of high traffic concentration. 
‘It is unlikely that Ontario has the worst air quality in the world, so the risks might be even higher in cities that are habitually wrapped in smog.’  
Professor Rob Howard of University College London added: ‘Regardless of the route of causation, this study presents one more important reason why we must clean up the air in our cities.’ 
Reference - BBC news 
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