90% of strokes can be prevented

Hypertension is the most important modifiable risk factor in reducing the burden of stroke, followed by high blood pressure

Just when you thought strokes can strike anyone at any time, a team of researchers report that 90%of them are preventable.

High blood pressure remains the single most important modifiable risk factor for stroke and the impact of hypertension and nine other risk factors together account for 90% of all strokes, according to an analysis of nearly 27000 people from every continent in the world.

Although the same ten risk factors were important and together accounted for 90% of stroke risk in all regions, the relative role of some individual risk factors varied by region, which the authors say should influence the development of strategies for reducing stroke risk.

The study led by Dr Martin O'Donnell and Prof Salim Yusuf of the McMaster University, along with collaborators from 32 countries, builds on preliminary findings from the first phase of the INTERSTROKE study, which identified ten modifiable risk factors for stroke in 6000 participants from 22 countries.

O'Donnell noted, "This study is of an adequate size and scope to explore stroke risk factors in all major regions of the world, within key populations and within stroke subtypes. The wider reach confirms the ten modifiable risk factors associated with 90% of stroke cases in all regions, young and older and in men and women. The study confirms that hypertension is the most important modifiable risk factor in all regions, and the key target in reducing the burden of stroke globally."

To estimate the proportion of strokes caused by specific risk factors, the investigators calculated the population attributable risk for each factor. The PAR, which is an estimate of the overall disease burden that could be reduced if an individual risk factor were eliminated, was 47.9%for hypertension, 35.8% for physical inactivity, 23.2% for poor diet, 18.6% for obesity, 12.4%for smoking, 9.1%for cardiac (heart) causes, 3.9% for diabetes, 5.8% for alcohol intake, 5.8% for stress, and 26.8% for lipids.

Many of these risk factors are known to also be associated with each other (e.g. obesity and diabetes), and when combined together, the total PAR for all ten risk factors was 90.7%, which was similar in all regions, age groups and in men and women.

Interestingly, the importance of some risk factors appeared to vary by region. For example, the PAR for hypertension ranged from 38.8%in western Europe, North America and Australia to 59.6% in Southeast Asia, the PAR for alcohol intake was lowest in western Europe, North America, Australia and highest in Africa (10.4%) and south Asia (10.7%), while the PAR for physical inactivity was highest in China.

Atrial fibrillation (irregular heart rhythm) was significantly associated with ischaemic stroke (PAR ranging from 3.1% in south Asia to 17.1% in western Europe, North America, and Australia), as was a high apolipoprotein [ApoB]/A1 ratio (PAR ranging from 24.8% in western Europe, North America, and Australia to 67.6% in southeast Asia).

Yusuf added, "Our findings will inform the development of global population-level interventions to reduce stroke, and how such programmes may be tailored to individual regions, as we did observe some regional differences in the importance of some risk factors by region. This includes better health education, more affordable healthy food, avoidance of tobacco and more affordable medication for hypertension and dyslipidaemia."