Almost one in three strokes are triggered by air pollution, alarming research has revealed.
The worldwide study named the environmental hazard as a major cause of one of the leading causes of death for the first time.
Air pollution, both inside from cooking fires and outside from traffic fumes, ranked among the top ten causes of stroke, along with better known risks such as smoking, high blood pressure and obesity.
Microscopic particles, much of which is generated by diesel exhausts, have been shown to cause clotting, which can lead to a stroke.
Stroke claims six million lives annually and many survivors suffer paralysis, speech problems and personality changes as a result.
Air pollution, both inside from cooking fires and outside from traffic fumes, causes a third of strokes
The New Zealand-led research analysed data from 188 countries to estimate the proportion of strokes that could be avoided if certain risks were avoided.
It found 70 per cent of strokes could be prevented by lifestyle changes such as giving up cigarettes, eating more fruit and vegetables and doing more exercise.
Overall, 30 per cent of of global disability associated with stroke is linked to air pollution.
This is especially high in developing countries where the burden is 33.7 per cent compared to 10.2 per cent in developed countries.
In low and middle-income nations in Asia and Africa, almost a fifth of stroke burden was attributed to household air pollution, while a similar percentage was blamed on outside air pollution in China and India.
In 2013, 17 per cent of global stroke cases were attributed to environmental air pollution, the Lancet Neurology study revealed.
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This is measured by tiny particles of soot or dust from traffic fumes and factories, fine particle matter known as PM 2.5.
This was almost as much as that from smoking (21 per cent).
In the UK levels have been illegally high in 16 cities since 2010, raising the risk of unhealthy blood vessels.
‘A striking finding of our study is the unexpectedly high proportion of stroke burden attributable to environmental air pollution, especially in developing countries,’ said study co-author Valery Feigin of New Zealand’s Auckland University of Technology.
Professor Vladimir Hachinski, of the University of Western Ontario, reviewed the research.
He said: ‘The most alarming finding was that about a third of the burden of stroke is attributable to air pollution.
Microscopic particles, much of which is generated by diesel exhausts, have been shown to cause clotting, which can lead to a stroke
‘Although air pollution is known to damage the lungs, heart, and brain, the extent of this threat seems to have been underestimated.
‘Air pollution is not just a problem in big cities, but is also a global problem.
‘With the ceaseless air streams across oceans and continents, what happens in Beijing matters in Berlin.’
He added: ‘Air pollution is one aspect of the fossil fuel and global warming problem, which is itself partly a result of westernisation and urbanisation, especially in India and China.
EXERCISING IN YOUR 40s ‘SLASHES THE RISK OF STROKE’
Being fit in your 40s could cut your risk of a stroke in your 60s.
Research has shown that men and women who are very fit in their mid to late 40s are a third less likely to suffer a stroke aged 65-plus than their couch-potato friends and colleagues.
The University of Texas researchers analysed data on almost 20,000 men and women.
These people had been put through a fitness test on a treadmill between the ages of 45 and 50 and had their health tracked until they were at least 65.
The fittest 40 per cent in middle-age were 37 per cent less likely than the least fit to suffer a stroke in old age.
The result held even when factors such as diabetes and high blood pressure were taken into account.
Writing in the journal Stroke, they said that exercise may boost blood flow to the brain, staving off the natural decay of brain tissue.
‘In 1900, only about 15 per cent of the world’s population lived in cities; now more than half the world’s population does.
‘In cities, particularly in megacities with more than10 million inhabitants, getting unhealthy food is easy and getting exercise is hard, emphasising the difficulty of achieving a healthy lifestyle in an unhealthy environment.’
Professor Feigin said it was now the responsibility of governments to address these stroke triggers through legislation and taxation of tobacco, alcohol, salt, sugar and saturated fat content.
Health service providers such as the NHS must also to check and treat risk factors for a stroke such as high blood pressure, she added.
Dr Shamim Quadir of the Stroke Association added: ‘The findings also suggest the priority in high income countries should be to encourage people to make lifestyle changes, such as stopping smoking, eating a balanced diet and taking regular exercise.
‘We know from previous research that taking these simple steps can help keep blood pressure under control, and greatly reduce your risk of having a stroke.
Dr Tim Chico, consultant cardiologist at the University of Sheffield, said: ‘Although there is always some uncertainty about such estimates, this study represents probably the most comprehensive attempt at understanding the extent to which multiple risk factors promotes stroke and other diseases.
‘For me, the most relevant finding to the UK is that around 70 per cent of strokes are associated with things that an individual can address – smoking, low levels of physical activity, and poor diet.’