Washington, Mar 7 : People with high blood pressure face an increased risk of intracerebral stroke i.e. a blood vessel bursting inside the brain. Now, researchers have found that smoking may worsen this risk.
Koshi Nakamura, M.D., Ph.D., lead author of the study, said that while smoking and high BP individually increase the risk of intracerebral stroke or hemorrhagic stroke, together they are even more dangerous.
"Smoking and high blood pressure both increase the risk of hemorrhagic stroke. Since we found that these two risk factors have a synergistic effect, quitting smoking and lowering blood pressure will contribute more to preventing stroke than if this previously unreported interaction is ignored," Dr. Nakamura said.
As a part of the study, Dr. Nakamura and his colleagues studied data on 563,144 people (82 percent Asian, 35 percent women, and average age 47) in the Asia Pacific Cohort Studies Collaboration (APCSC) to examine whether smoking increased the risk of stroke and coronary heart disease in people with high blood pressure.
37 percent 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.
Based on this, the researchers concluded that for every 10 mm Hg increase in systolic blood pressure, smokers faced an 81 percent increase in hemorrhagic stroke risk, while nonsmokers faced a 66 percent increase in risk - a 15 percentage point increased risk in smokers than nonsmokers.
Systolic blood pressure (SBP) is the pressure when the heart beats. Normal blood pressure is defined as SBP below 120 mm Hg and DBP below 80 mm Hg.
This effect of smoking on blood pressure was specific to hemorrhagic stroke as there was no evidence to indicate a similar effect on the risk of coronary heart disease or ischemic stroke, researchers said.
The researchers suggest that a reason why smoking may exacerbate the risk of hemorrhagic stroke is because smoking may damage blood vessels in the brain that are already weakened by high BP.
Weakened blood vessels are prone to rupture and bleeding and hence are particularly susceptible to hemorrhagic stroke.
"Hemorrhagic stroke is an especially debilitating stroke as about half of the people who have one die as a result of it, while many survivors are left with paralysis or other debilitating effects," said Rachel Huxley, D.Phil., a study co-author.
The study appears in the journal Stroke: Journal of the American Heart Association.