Stroke is largely preventable, with hypertension confirmed as biggest risk factor, according to global study

http://www.eurekalert.org/pub_releases/2016-07/tl-tls071416.php

Public Release: 15-Jul-2016
The Lancet: Stroke is largely preventable, with hypertension confirmed as biggest risk factor, according to global study
10 potentially modifiable risk factors account for 90 percent of strokes worldwide, but regional variation should be considered, says study
The Lancet

Hypertension (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 (INTERSTROKE), published in The Lancet.

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.

Stroke is a leading cause of death and disability, particularly in low-income and middle-income countries. The two major types of stroke include ischaemic stroke (caused by blood clots), which accounts for 85% of strokes, and haemorrhagic stroke (bleeding in the brain), which accounts for 15% of strokes. Prevention of stroke is a major public health priority, but needs to be based on a clear understanding of the key preventable causes of stroke.

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To estimate the proportion of strokes caused by specific risk factors, the investigators calculated the population attributable risk for each factor (PAR; an estimate of the overall disease burden that could be reduced if an individual risk factor were eliminated [4]). The PAR 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 (the study used apolipoproteins, which was found to be a better predictor of stroke than total cholesterol). 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).

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