Air pollution, including environmental and household air pollution, has emerged as the leading risk factor for stroke globally, finds a new study.

This is especially high in developing countries-33.7 per cent vs 10.2 per cent in developed countries, the researchers said.

From 1990 to 2013, stroke associated with environmental air pollution showed an increase by over 33 per cent worldwide. However, second-hand smoke saw a decrease by 31 per cent between the same period. 

"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 Valery L Feigin, Professor at Auckland University of Technology in New Zealand. 

Also, over 90 per cent of the global burden of stroke was caused by modifiable risk factors and 74 per cent of them are behavioural risk factors such as smoking, poor diet and low physical activity. 

"Controlling these risk factors could prevent about three-quarters of strokes worldwide," Feigin added.

Further, air pollution, environmental risks, tobacco smoke, high blood pressure and dietary risks were the other risk factors found for stroke in developing countries compared to developed countries.

Household air pollution was found to be an important risk factor for stroke in central, eastern and western sub-Saharan Africa as well as south Asia.

Every year, approximately 15 million people worldwide suffer a stroke. High blood pressure, diet low in fruit, high body mass index (BMI), diet high in sodium, smoking, diet low in vegetables, environmental air pollution, household pollution from solid fuels, diet low in whole grains and high blood sugar were found as the ten major risk factors for stroke. 

"Our findings are important for helping national governments and international agencies to develop and prioritise public health programmes and policies," Feigin noted.

For the study, published in The Lancet Neurology journal, the team used data from the Global Burden of Disease Study to estimate the disease burden of stroke associated with 17 risk factors in 188 countries between 1990-2013. 

"Air pollution is not just a problem in big cities, but is also a global problem. It 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," the researchers concluded.