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18-07-2016 | Stroke | News | Article

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Expanded INTERSTROKE confirms global hypertension impact

medwireNews: Hypertension accounts for around half of all strokes in all regions of the world, show the results of the second phase of INTERSTROKE.

This latest phase of the case–control study includes data from 142 centres in 32 countries in all global regions – 10 more than in the first phase – and includes 26,919 participants, making it more than fourfold larger. Of the 13,447 stroke cases, 77.3% had ischaemic stroke and 22.7% intracerebral haemorrhage (ICH).

The expanded study, which appears in The Lancet, “lends a greater generalisability to the original INTERSTROKE results”, said lead researcher Martin O’Donnell (McMaster University, Ontario, Canada) in a press statement.

The same 10 risk factors identified in the first phase accounted for between 82.7% (in Africa) and 97.4% (in Southeast Asia) of all strokes. Again, hypertension was by some distance the strongest risk factor, with a population-attributable risk (PAR) of 45.7% for ischaemic stroke and 56.4% for ICH.

And the effect of hypertension was consistent throughout the regions studied, with PARs exceeding 40% for everything except ICH in Western Europe, North America and Australia, which was 25.2%. Its effects were also consistent in people older and younger than 55 years.

“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”, said O’Donnell.

Physical activity was the second most impactful factor, with PARs of 33.4% and 34.6% for ischaemic stroke and ICH, respectively.

Another five of the 10 risk factors – waist-to-hip ratio, diet, alcohol intake, cardiac causes and psychosocial factors – predicted both ischaemic and haemorrhagic stroke. But smoking, diabetes and the ratio of apolipoprotein B to A-1 were associated with ischaemic stroke only.

“Therefore, although a broader array of targets exists for prevention of ischaemic stroke than for intracerebral haemorrhage, a more marked reduction in intracerebral haemorrhage is expected by the reduction of blood pressure alone”, says the team.

This second study phase, with higher statistical power, revealed some variations between regions. For example, the PAR for apolipoproteins was markedly higher in Southeast Asia (66.7%) than in other regions (20.4–49.7%), as was the PAR for psychosocial factors in China (30.6 vs 2.6–17.3%).

The effects of diet varied widely across regions; poor diet actually appeared to have a protective effect in Southeast Asia, which the researchers say “raise[s] caution about the generalisability of diet risk scores developed in North America and Europe to other regions.”

Alcohol intake also had highly variable effects, potentially because of “variations in patterns and types of alcohol consumed”.

“Despite these differences, the collective contribution of these ten risk factors to stroke risk was consistent in all populations, meaning that general approaches to prevention of stroke can be similar worldwide, but population-specific refinement of programmes might be needed”, the team concludes.

By Eleanor McDermid

medwireNews is an independent medical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2016