Analyzing data on 6,000 people — half of whom suffered a stroke, and half of had not — from 22 countries around the globe, researchers from Canada’s McMaster University identified 10 common risk factors, including smoking, high blood pressure and belly fat, associated with 9 out of 10 strokes. The results of the INTERSTROKE study, as it it’s known, are being presented this week at the World Congress of Cardiology in Beijing and will be published in The Lancet.
For the study, all participants completed detailed questionnaires about medical history and behavior and underwent a physical exam. Stroke patients were assessed by researchers within three days of hospital admission, and within five days of the first onset of stroke symptoms. Participants in the control group were matched by age and gender, and had no history of stroke themselves.
Researchers found that 80% of all strokes were associated with five common risk factors: hypertension (high blood pressure), smoking, poor diet, belly fat, and low physical activity. When researchers examined five additional risk factors — diabetes, heart disease, alcohol consumption, high cholesterol and stress or depressive symptoms — they found that together, these 10 risk factors were linked to 90% of the population-attributable risk (a measure of the population-wide impact of risk) for all strokes.
When the study authors analyzed risk factors by particular type of stroke, they found that all 10 of these major factors were strongly associated with ischemic stroke, or when a clot in a blood vessel blocks blood and oxygen supply to the brain. They found that five risk factors were more pronounced for intracerebral hemorrhage, or bleeding within the brain: high blood pressure, smoking, belly fat, poor diet and alcohol consumption.
Considering each risk factor individually, the researchers found that hypertension was the most significant risk factor for stroke, as it was associated with roughly one third of all risk for stroke.