A study has, for the first time, pinpointed air pollution as a leading risk factor for stroke worldwide.

Published in The Lancet Neurology journal, the new study also reported that air pollution (including environmental and household air pollution) is associated with about a third of the global burden of stroke in 2013.

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It was the first to analyze the global risk factors for stroke in minute detail, especially in relation to stroke burden on global, regional and national levels. Researchers used data from 1990 to 2013 in the Global Burden of Disease Study to estimate the disease burden of stroke associated with 17 risk factors in 188 countries.

Not surprisingly, it showed that over 90% of the global burden of stroke is linked to modifiable risk factors. Most of these modifiable risk factors (74%) are behavioral risk factors such as smoking, poor diet and low physical activity.

The study authors estimate that control of these risk factors might prevent about three-quarters of all strokes.

Every year, some 15 million people worldwide suffer a stroke. Of this total, nearly six million die and five million are left with permanent disability. Disability may include loss of vision and/or speech, paralysis and confusion.

Globally, the 10 leading risk factors for stroke are high blood pressure, high blood sugar, smoking, high body mass index (BMI), diet low in fruit, diet high in sodium, diet low in vegetables, environmental air pollution, household pollution from solid fuels and diet low in whole grains.

About a third (29.2%) of global disability associated with stroke is linked to air pollution (including environmental air pollution and household air pollution). This is especially high in developing countries (33.7% vs. 10.2% in developed countries).

In 2013, 16.9% of the global stroke burden was attributed to environmental air pollution (as measured by ambient particle matter (PM) pollution of aerodynamic diameter smaller than 2·5 μm) -- almost as high as that from smoking (20.7%).

From 1990 to 2013, stroke burden associated with environmental air pollution (PM25) increased by over 33%.

Air pollution, environmental risks, tobacco smoke, high blood pressure and dietary risks were more important risk factors for stroke in developing countries compared to developed countries.

Low physical activity was a more important risk factor for stroke in developed countries compared to developing countries.

"A striking finding of our study is the unexpectedly high proportion of stroke burden attributable to environmental air pollution, especially in developing countries," said lead author Professor Valery Feigin of Auckland University of Technology, New Zealand.

"Our findings are important for helping national governments and international agencies to develop and prioritize public health programs and policies. Governments have the power and responsibility to influence these risk factors through legislation and taxation of tobacco, alcohol, salt, sugar or saturated fat content, while health service providers have the responsibility to check and treat risk factors such as high blood pressure," he said.

Tagsstroke, air pollution, Global Burden of Disease Study