Some 90% of strokes worldwide are potentially preventable, a new study involving Irish scientists has confirmed.

According to the findings, 10 potentially modifiable risk factors account for 90% of all strokes globally, with high blood pressure (hypertension) still the biggest risk factor.

The study was based on an analysis of almost 27,000 people from every continent in the world.

Every year in Ireland, some 10,000 people suffer a stroke and 2,000 people die as a result. Thousands more are left with stroke-related disabilities

A stroke occurs when the blood supply to the brain is interrupted, depriving it of oxygen. As a result, some of the brain cells die and others are damaged. One in six people will have a stroke at some stage in their life and 85% are known as ischaemic strokes. These are strokes caused by a sudden blockage in the blood vessels supplying the brain, by a blood clot.

The prevention of stroke is a major public heath issue.

According to one of the lead researchers, Dr Martin O'Donnell, of NUI Galway and McMaster University in Ontario, Canada, 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 10 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," he explained.

The researchers calculated the population attributable risk (PAR) for each risk factor - this is an estimate of the overall disease burden that could be reduced if an individual risk factor was eliminated.

The study found that the PAR for high blood pressure was just under 48%. This was followed by physical inactivity (35%), lipids (fats) in the blood (26%), poor diet (23%), obesity (18%), smoking (12%), heart-related causes (9%), alcohol intake (just under 6%), stress (just under 6%) and diabetes (just under 4%).

Some of these risk factors are known to be linked with each other, e.g. if you are obese, you have an increased risk of developing diabetes. However overall, when combined together, the total PAR for the 10 risk factors was 90%.

The researchers did note that the importance of some risk factors varied depending on the part of the world. For example, the PAR for high blood pressure ranged from 38% in parts of the world, including western Europe, to almost 60% in southeast Asia.

The study's other lead researcher, Prof Salim Yusuf, of McMaster University, said that the findings show ‘that the majority of stroke is due to common modifiable risk factors'.

"This is the first study that is adequately powered to explore stroke risk factors in all regions of the world and between stroke subtypes. It confirms the 10 modifiable risk factors associated with 90% of stroke cases and it also confirms that hypertension is the most important modifiable risk factor in all regions," he said.

Details of these findings are published in the journal, The Lancet.