Strike against stroke

16 July 2016

Published in The Lancet: Australian data has been used for the first time in a study on the risk factors for stroke-related death and injuries across ethnic groups. It suggests that almost half of the global stroke burden could be prevented through better control of blood pressure.

The study extends a previous INTERSTROKE study of 6000 people from 22 countries, which had identified ten modifiable risk factors for stroke. Together, the results from the full INTERSTROKE study draws on data from nearly 27000 people from every continent.

The research addressed the two types of stroke: ischaemic stroke, which is caused by blood clots and accounts for around 85% of strokes, and haemorrhagic strokes, which caused by a bleeding in the brain.

The research not only confirmed the ten risk factors of stroke, which together account for 90% of strokes, it also assessed the proportion by which each of the individual risk factors contributes to the disease.

This was done by calculating how much the occurence of stroke could be reduced if a risk factor was reduced - measured as the population attributabel risk or PAR.

Hypertension was the single most important modifiable risk factor for stroke followed by physical inactivity, increasing the risk of stroke by 48% and 36%, respectively.

The ten risk factors for stroke and their assessed PAR values across populations were:

While the INTERSTROKE study revealed that the majority of stroke is caused by common modifiable risk factors, it also found that the importance of individual risk factors somewhat varies from region to region. For example, the researchers found that hypertension increased the risk by 40% in Australians, western Europeans and North Americans, but by 60% in Southeast Asians.

The PAR for alcohol intake was significantly lower in western Europe, North America and Australia than in Africa, and the PAR for physical inactivity was found highest in China. Similar differences were found for other risk factors.

According to the authors, this finding should influence the development of global population-level strategies - e.g. better health education, more affordable healthy food, avoidance of tobacco and more affordable medication for hypertension and dyslipidaemia - with programs potentially being tailored to individual regions.

A commentary by scientists from the University of Technology, Auckland, published in the same issue of The Lancet, points out that the INTERSTROKE study has three key messages: (1) stroke is a highly preventable disease globally; (2) the associated risk factors require a regional or ethnic-specific approach; and (3) additional research is needed for countries and ethnic groups not included in the study.

"We have heard the calls for actions about primary prevention. Now is the time for governments, health organisations, and individuals to proactively reduce the global burden of stroke. Governments of all countries should develop and implement an emergency action plan for the primary prevention of stroke."