High blood pressure poses greatest stroke risk - study

Smoking, poor diet and an expanded waistline are included in a check-list of 10 risk factors most closely associated with stroke, experts revealed today.

Together, the list of harmful conditions and behaviours accounted for 90% of stroke risk.

They were identified by researchers involved in the Interstroke study looking at the lifestyle and biological factors that contribute to stroke in 22 countries.

The Canadian-led scientists analysed data from 3,000 patients who suffered their first stroke between March 2007 and April 2010.

Their personal details were compared with those of a “control” population of 3,000 healthy individuals.

The 10 key risk factors were: high blood pressure, current smoking, abdominal obesity, poor diet, lack of physical exercise, diabetes, excess alcohol consumption, stress and depression, heart disorders, and the presence of blood fat molecules called apolipoproteins.

Five lifestyle-linked factors – high blood pressure, smoking, abdominal obesity, diet and physical activity – accounted for more than 80% of the worldwide risk of stroke on their own.

Most of the risk factors mirrored those associated with heart attacks, previously highlighted in another study called Interheart.

The results were published online today by The Lancet medical journal.

Dr Martin O’Donnell, from McMaster University in Hamilton, Ontario, and colleagues wrote: “Our findings suggest that 10 risk factors are associated with 90% of the risk of stroke. Targeted interventions that reduce blood pressure and smoking, and promote physical activity and healthy diet, could substantially reduce the burden of stroke.”

Of all the factors, high blood pressure was by far the most important, accounting for a third of all stroke risk.

People who had a history of high blood pressure were more than two and a half times more likely to suffer a stroke than those who did not.

Smoking was another major hazard, the study found, and associated with one in five strokes. Smokers had double the stroke risk of non-smokers.

Each year an estimated 150,000 people have either a full-blown or “mini” stroke for the first time in the UK.

Around a third of these patients die, a third recover, and a third are left with a serious disability.

Writing in The Lancet, Dr Jack Tu, from the Institute for Clinical Evaluative Sciences at the University of Toronto in Canada, said: “Whilst hypertension (high blood pressure) is well established as the most important cause of stroke in high-income countries, Interstroke confirms that it is also the most important risk factor for stroke in developing countries.

“This finding is particularly relevant because it highlights the need for health authorities in these regions to develop strategies to screen the general population for high blood pressure, and, if necessary, offer affordable treatment.

“It also provides an impetus to develop population-wide strategies to reduce the salt content in the diet of individuals in these countries.”

Phase II of Interstroke, now under way, aims to include 20,000 participants and will look at the importance of risk factors within different regions and ethnic groups. It will also study genetic links to the risk of stroke.

Andrea Lane, from The Stroke Association, said: “Over the years there have been a number of research studies into the causes of stroke, which have identified a number of major risk factors.

“This is an extensive and in-depth study and so it’s great to see that the findings support previous research and reflect the preventative advice provided by The Stroke Association.

“The study is interesting as it looks at the major risk factors for stroke worldwide, including low and middle income countries. We look forward to seeing the results from the second phase of the research.”