Most Strokes Are Attributable to Modifiable Risk Factors

More than 90% of the stroke burden is attributable to modifiable risk factors, and achieving control of behavioral and metabolic risk factors could avert more than 75% of the global stroke burden, according to a new study.

“Thus, this further justifies the need to focus on primary prevention,” said lead study author Valery Feigin, MD, PhD, director of the National Institute for Stroke and Applied Neurosciences in New Zealand.
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The researchers used data on stroke-related disability-adjusted life-years (DALYs), risk factors, and population-attributable fraction from the Global Burden of Disease Study 2013 to estimate the burden of stroke by age and sex (with corresponding 95% uncertainty intervals [UI]) in 188 countries, as measured with stroke-related DALYs in 1990 and 2013.

They evaluated attributable DALYs for 17 risk factors (air pollution and environmental, dietary, physical activity, tobacco smoke, and physiological) and 6 clusters of risk factors by use of 3 inputs: risk factor exposure, relative risks, and the theoretical minimum risk exposure level.

For most risk factors, they synthesized data for exposure with a Bayesian meta-regression method or spatial-temporal Gaussian process regression. The investigators based relative risks on meta-regressions of published cohort and intervention studies. Attributable burden for clusters of risks and all risks combined took into account evidence on the mediation of some risks, such as high body mass index (BMI), through other risks, such as high systolic blood pressure and high total cholesterol.

Feigin said other key findings include:

• The burden of stroke attributable to these risk factors has greatly increased from 1990-2013, suggesting the prevalence of these risk factors has increased dramatically over this time period.
• Almost three-quarters (74.2%) of the stroke burden is attributable to behavioral risks, such as poor diet, smoking, and low physical activity, and the contribution of these behavioral risks is even greater than the contribution of metabolic risks (72.4%), such as high systolic blood pressure, high BMI, high fasting plasma glucose, high total cholesterol, and low glomerular filtration rate. “This means that stroke now is more a disease of the lifestyle,” he said.
• In the most surprising discovery, about 30% of the global stroke burden is linked to air pollution (ambient PM2.5 pollution and household air pollution from solid fuels combined).

“The main clinical implication of our findings is that 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,” Feigin said. “The main public health implication of our findings is there is the urgent need for focused primary stroke prevention strategies being implemented on a community level. These population-wide preventative strategies should be prioritized based on the proportional contribution of various risk factors and risk factor clusters. In developing countries, reducing exposure to air pollution should be one of the main priorities in primary stroke prevention.”

–Mike Bederka

Reference:

Feigin VL, Roth GA, Naghavi M, et al; Global Burden of Diseases, Injuries and Risk Factors Study 2013 and Stroke Experts Writing Group. Global burden of stroke and risk factors in 188 countries, during 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013 [published online June 9, 2016]. Lancet Neurol. doi:10.1016/S1474-4422(16)30073-4.