Air Pollution Joins List of Leading Causes of Stroke Worldwide

Nine out of every 10 strokes around the globe are caused by potentially modifiable risk factors, with about three-quarters of the burden related to behavioral and metabolic factors and about one-third due to environmental factors—notably, air pollution. The findings, from a study of 188 countries, indicate that stroke is largely a disease of lifestyle.

“Stroke burden is highly avoidable,” lead author Valery Feigin, MD (Auckland University of Technology, New Zealand), told TCTMD in an email. “Far greater attention must be paid by doctors and other health service providers to controlling hazardous behavioral risk factors irrespective of the baseline absolute cardiovascular risk, age, or sex of the patients.”

Moreover, he said, worldwide, “urgent primary stroke preventative strategies integrated with primary prevention strategies of other major noncommunicable diseases that share common risk factors with stroke (such as dementia, heart attack, diabetes mellitus, cancer) should be implemented.”

And because air pollution has emerged as a leading contributor to stroke burden, particularly in the developing world, he said, “measures to reduce air pollution should be one of the main priorities for combating stroke.”

The findings were published online June 9, 2016, ahead of print in the Lancet Neurology.

Urgent Need for Prevention Strategies

Feigin and colleagues used data from the Global Burden of Disease Study 2013 to estimate the contribution—measured by the population-attributable fraction—of 17 environmental, occupational, behavioral, physiological, and metabolic risk factors and six clusters of risk factors to global stroke burden between 1990 and 2013.

They found that behavioral factors like smoking, poor diet, and low physical activity accounted for 74.2% of stroke cases and that a host of metabolic risk factors, including high blood pressure, body mass index, fasting plasma glucose, and total cholesterol and poor renal function, contributed to 72.4%.

Environmental factors accounted for 33.4% of the stroke burden, with air pollution alone contributing to 29.2% of cases.

The burden of almost all risk factors increased from 1990 to 2013, with the exception of secondhand smoking and household air pollution from solid fuels, which both declined.

Feigin said that the increase over time in the burden attributable to most risk factors was surprising, and suggests that the prevalence of those factors also rose during that time.

“This makes a very strong case for urgent implementation of both population-wide and high-risk primary prevention strategies across the globe,” he said.

In an accompanying editorial, Vladimir Hachinski, MD, and Mahmoud Reza Azarpazhooh, MD (University of Western Ontario, London, Canada), agree that the “study provides a firm basis for policy makers to implement preventative measures.”

They identify the burden attributable to air pollution as “the most alarming finding.”

“Although air pollution is known to damage the lungs, heart, and brain, the extent of this threat seems to have been underestimated,” they write. “Air pollution is not just a problem in big cities, but is also a global problem.”

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