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Air pollution major worldwide risk factor for stroke
Nearly 30% of the global burden of stroke can be attributed to air pollution, researchers reported in The Lancet Neurology.
According to study data published by Valery L. Feigin, MD, MSc, PhD, FAAN, and colleagues, more than 90% of global stroke burden is related to modifiable risk factors, approximately 74% of which are behavioral risk factors including smoking, lack of physical activity and poor diet. The researchers estimated that if these behavioral risk factors could be controlled, approximately 75% of all strokes would be prevented.
Valery L. Feigin
“A striking finding of our study is the unexpectedly high proportion of stroke burden attributable to environmental air pollution, especially in developing countries,” Feigin, from Auckland University of Technology, New Zealand, said in a press release. “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.”
The researchers used data from the Global Burden of Disease Study 2013 on stroke-related disability-adjusted life years (DALYs), risk factors and population-attributable fractions to calculate age- and sex-adjusted burden of stroke in 188 countries.
Feigin and colleagues evaluated DALYs attributable to 17 risk factors and six clusters of risk factors, and they calculated relative risks based on meta-regressions of existing cohort and intervention studies.
An administrative record system also was used to observe risks related to diet and alcohol consumption. Due to a lack of data, certain factors could not be included, such as atrial fibrillation, substance abuse, patterns related to smoking, BMI or underlying genetic risk factors.
According to the researchers, 90.5% (95% uncertainty interval [UI], 88.5-92.2) of stroke burden as expressed by DALYs could be attributed to the modifiable risk factors analyzed. Of this burden, 74.2% could be attributed to behavioral factors.
The second largest contributor to DALYs was metabolic factors, including high systolic BP, high BMI, high fasting plasma glucose, high total cholesterol and low glomerular filtration rate (burden, 72.4%; 95% UI, 70.2-73.5), according to the researchers.
The third largest contributor to DALYs was environmental factors including air pollution and lead exposure (burden, 33.4%; 95% UI, 32.4-34.3), and 29.2% (95% UI, 28.2-29.6) of the global burden of stroke could be attributed to air pollution, Feigin and colleagues wrote.
Stroke burden due to behavioral, environmental and metabolic risk clusters did not significantly differ by sex, but the population-attributable fraction of behavioral risk factors was greater for men in low- to middle-income countries.
In high-income countries, the five greatest risk factors for DALYs were high systolic BP, high BMI, diet low in fruits, diet low in vegetables, and smoking. In these countries, the researchers wrote, metabolic and behavioral risk factors were the two leading causes of stroke-related DALYs, accounting for 15.2 million (70.7%) and 15 million (69.5%) DALYs, respectively.
The five leading risk factors in middle- to low-income countries were high systolic BP, diet low in fruit, diet high in sodium, high BMI and smoking. Factors that contributed to DALYs included behavioral (75.4%), metabolic (72.8%) and environmental risks including pollution (38.6%), according to the researchers.
“Our findings are important for helping national governments and international agencies to develop and prioritize public health programs and policies,” Feigin said in the press release. “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 [BP].” – by Dave Quaile
Disclosure: Feigin reports that his institution holds the copyright to a stroke risk app, proceeds from which go to research and education on stroke prevention. Please see the full study for a list of the other researchers’ relevant financial disclosures.