A new study has found that smoking increases the risk of a hemorrhagic stroke for people with high blood pressure.

The study examined data on 563,144 people, with an average age 47, who took part in the Asia Pacific Cohort Studies Collaboration.

More than a third of the participants were smokers at the start of the study. During a median of 6.8 years of follow-up, 746 of the 210,961 smokers and 899 of the 352,183 nonsmokers suffered a hemorrhagic stroke, where a blood vessel bursts inside the brain.

Further analysis revealed that for every 10mm/Hg increase in systolic (when the heart beats) blood pressure, smokers faced an 81 percent increased risk of hemorrhagic stroke, compared with a 66 percent increased risk for nonsmokers.

This added risk of smoking in people with high blood pressure appeared to be specific to hemorrhagic stroke, as there was no evidence to indicate a similar effect on the risk of is chemic stroke (blocked blood flow to the brain) or coronary heart disease, according to the study published in the March issue of Stroke.

Smoking may further damage blood vessels in the brain that are already weakened by high blood pressure, said the study. Weakened blood vessels are prone to rupture and bleeding, thus increasing the risk of hemorrhagic stroke.

Smokers with the highest systolic blood pressure readings (150mm/ Hg or greater) were 9.32 times more likely to suffer hemorrhagic stroke than smokers with the lowest readings (120mm/Hgor less). Nonsmokers with the highest systolic blood pressure readings were 7.05 times more likely to suffer hemorrhagic stroke than those with the lowest readings.

(Xinhua News Agency March 9, 2008)