Living near a main road increases the risk of dementia, the first major research into air pollution and disease has shown. 

首项研究空气污染与疾病关系的重要调查发现，住在主干道旁边有可能增加患痴呆的风险。

A decade-long study of 6.6 million people, published in The Lancet, found that one in 10 dementia deaths in people living within 50 metres of a busy road was attributable to fumes and noise. 

There was a linear decline in deaths the further people lived away from heavy traffic. 

Air pollution is already known to contribute to the deaths of around 40,000 people in Britain each year by exacerbating respiratory and heart conditions, while previous research showed emissions can cause brain shrinkage. 

But the new study by Canadian public health scientists is the first to find a link between living close to heavy traffic and the onset of dementia, a discovery described as "plausible" and "impressive" by British experts. 

Dr Hong Chen, the lead author from Public Health Ontario, said: 

"Our study suggests that busy roads could be a source of environmental stressors that could give rise to the onset of dementia." 

"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." 

"More research to understand this link is needed, particularly into the effects of different aspects of traffic, such as air pollutants and noise. Around 850,000 people suffer from dementia in Britain, and it is now the leading cause of death for both men and women."