Lead scientist Dr Hong Chen analysed records of 6.5 million Ontario residents aged 20 to 85 and found 2,43,611cases of dementia between 2001and 2012. Then they mapped residents’ proximity to roadways using postal codes. The increase in the risk of developing dementia went down to 4% if people lived 50 to 100 metres from major traffic, and to 2% if they lived within 101 to 200 metres. At more than 200 metres, the elevated risk faded away .
“Air pollutants can get into the blood stream and lead to inflammation, which is linked with cardiovascular disease and diabetes. This study suggests pollutants that can get into the brain via the blood stream can lead to neurological problems,“ said Ray Copes, a health expert at Public Health Ontario, who conducted the study with colleagues from Institute for Clinical Evaluative Sciences.
Population growth and urbanisation has placed many people close to areas with heavy traffic, and with growing rates of dementia even a modest effect from near-road exposure can pose a large public health burden. Other results from the study suggested a connection between dementia and exposure to two common traffic pollutants, nitrogen dioxide and fi ne particles of sooty material generated by diesel engines.
The WHO estimates the number of people with dementia in 2015 at 47.5 million, and the number is rising rapidly as life expectancy increases and societies age. It is starting to overtake heart disease as a major cause of death in some developed countries. Tom Dening of the Centre for Old Age and Dementia in UK said, “It is unlikely that Ontario has the worst air quality in the world, so the risks might be even greater in cities that are habitually wrapped in smog.“