Air pollution, including environmental and household air pollution, has emerged as a leading risk factor for stroke worldwide - associated with about a third of the global burden of stroke in 2013 - according to a new study published in The Lancet Neurology journal.
The findings, from an analysis of global trends of risk factors for stroke between 1990-2013, also show that over 90 per cent of the global burden of stroke is linked to modifiable risk factors, most of which (74 per cent) are behavioural risk factors such as smoking, poor diet and low physical activity. The authors estimate that control of these risk factors could prevent about three-quarters of all strokes.
The study is the first to analyse the global risk factors for stroke in such detail, especially in relation to stroke burden on global, regional and national levels. The researchers used data from the Global Burden of Disease Study to estimate the disease burden of stroke associated with 17 risk factors in 188 countries. They estimated the population-attributable fraction (PAF) of stroke-related disability-adjusted life years (DALYs), ie the estimated proportion of disease burden in a population that would be avoided if exposure to a risk factor were eliminated.
Every year, approximately 15 million people worldwide suffer a stroke - of these, 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 were 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. About a third (29.2 per cent) 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 per cent vs 10.2 per cent in developed countries).
In 2013, 16.9 per cent 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 much as that from smoking (20.7 per cent). From 1990 to 2013, stroke burden associated with environmental air pollution (PM25) has increased by over 33 per cent.
"A striking finding of our study is the unexpectedly high proportion of stroke burden attributable to environmental air pollution, especially in developing countries. Smoking, poor diet and low physical activity are some of the major risk factors for stroke worldwide, suggesting that stroke is largely a disease caused by lifestyle risk factors. Controlling these risk factors could prevent about three-quarters of strokes worldwide." says lead author Professor Valery L Feigin, of Auckland University of Technology, New Zealand.
"Our findings are important for helping national governments and international agencies to develop and prioritise public health programmes 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 says.
"Taxation has been proven to be the most effective strategy in reducing exposure to smoking and excessive intake of salt, sugar and alcohol. If these risks take a toll on our health, and taxation is the best way to reduce exposure to these risks, it logically follows that governments should introduce such taxation and reinvest the resulting revenue back into the health of the population by funding much needed preventative programmes and research in primary prevention and health. All it takes is recognition of the urgent need to improve primary prevention, and the good will of the governments to act," says professor Feigin.