MedWire News: The INTERSTROKE study has identified 10 risk factors that account for 90% of the risk for stroke worldwide.
The risk factors were similar to the nine identified for myocardial infarction (MI) in the INTERHEART study, and most were modifiable.
“Targeted interventions that reduce blood pressure and smoking, and promote physical activity and a healthy diet, could substantially reduce the global burden of stroke,” say Martin O’Donnell (McMaster University, Hamilton, Ontario, Canada) and team.
However, the relative importance of the risk factors appeared to vary between stroke and MI. “On the basis of an indirect comparison between the studies, these differences are most notable for hypertension, apolipoproteins, physical activity, and alcohol intake,” the researchers note in The Lancet.
They add: “These findings are important to help guide optimum selection of risk-factor targets for population-based programs to prevent all cardiovascular diseases.”
The team’s conclusions are based on an analysis of 3000 stroke patients, 78% with ischemic and 22% with hemorrhagic stroke, from 22 countries worldwide, who had undergone routine neuroimaging.
The researchers established the prevalence of vascular risk factors in the patients, and in 3000 age- and ethnicity- matched controls, by interview and examination.
History of hypertension was the most important risk factor for stroke, they report, being 2.69 times more likely to be present in cases than controls. The association was stronger if hypertension was defined as a history of the condition or blood pressure exceeding 160/90 mmHg.
The addition of another four risk factors – smoking status, waist-to-hip ratio, diet risk score, and regular physical activity – gave a population-attributable risk (PAR) of 83.4%. In other words, these five risk factors explained 83.4% of the stroke risk in the study population.
Notably, body mass index was not associated with stroke risk.
The PAR increased to 90.3% with the addition of diabetes, alcohol intake, psychosocial factors, cardiac causes, and the ratio of apolipoprotein B to A-1 – 10 risk factors in all.
The latter lipid ratio was not associated with hemorrhagic stroke, but the other nine factors together gave a PAR of 90.8% for hemorrhagic stroke.
O’Donnell et al stress the importance of hypertension, saying that it is more significant than other “objectively measured” risk factors; in other words, lipid and glucose levels.
“Of these three risk factors, blood pressure is arguably the most amenable to change in low-income settings because screening programs need modest equipment and little specialized expertise,” they say.
“Additionally, blood pressure is readily reduced by inexpensive generic drugs and nonpharmacological approaches (eg, salt reduction).”
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