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Smoking stokes risk for bleeding strokes

July 1, 1993

Smoking stokes risk for bleeding strokes

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DALLAS—Men who smoke increase their risk for hemorrhagic stroke every time they light up, and smoking more than a pack of cigarettes a day doubles their risk compared with nonsmokers or men who’ve kicked the habit, according to a long-term prospective study reported in today’s rapid access issue of Stroke: Journal of the American Heart Association.

Hemorrhagic strokes are caused by ruptured blood vessels bleeding in the brain. According to the American Heart Association, hemorrhagic strokes account for about 12 percent of all strokes, and 37.5 percent of them result in death within 30 days.

Smoking is already identified as a risk factor for ischemic stroke—the most common type of stroke, caused when the blood supply to the brain is blocked. Smoking is also linked with subarachnoid hemorrhage (SAH)—a stroke characterized by bleeding into the space between the brain and the skull. The relationship between smoking and intracerebral hemorrhage (ICH)—bleeding inside the brain—had not been clearly established, says lead investigator Tobias Kurth, M.D., SCs., instructor of medicine, Brigham and Women’s Hospital, Harvard Medical School in Boston.

In this stydy of 22,022 U.S. male physicians followed for almost 18 years, current smokers had a greater risk for all types of hemorrhagic strokes. Current smokers were 1.7 times more likely to have hemorrhagic stroke if they smoked less than 20 cigarattes a day and 2.4 times more likely if they smoked more than 20 cigarettes a day when compared men who never smoked.

In particular, the risks for ICH were also significant.

“Overall, current smokers had about a twofold increase in risk for ICH. Moreover, the more one smokes, the worse it gets. The risk of ICH increased from 1.6 times more likely than never-smokers for men who smoked less than a pack a day to 2.1 times more likely than never-smokers for men who smoked 20 or more cigarettes a day,” Kurth says.

Researchers found that the risk for ICH is the same for men who’d never smoked and for former smokers, so it can be inferred that quitting decreases risk. However, this study couldn’t specifically measure how fast the risk goes down, he says.

The study subjects were participants in the Physicians’ Health Study, a completed randomized trial that tested the effect of low-dose aspirin on cardiovascular risk. Enrollment began in 1982 and participants (92 percent white) ranging in age from 40 to 84 at enrollment—were followed until March 2002. Baseline information was collected via mail questionnaire, with follow-up questionnaires every year. Information on smoking habits was collected at baseline, 24 months, 60 months and 144 months.

At baseline, 49.6 percent of the participants said they never smoked, and 39.4 percent said they were past smokers. Almost 4 percent said they currently smoked less than a pack a day, and 7.1 percent said they currently smoked at least a pack a day.

During an average follow-up of 17.8 years, 1,069 strokes were reported, including 139 hemorrhagic strokes. Of the smaller group, 108 were ICH, and 31 were SAH.

Compared with never smokers, past smokers had no increased risk for hemorrhagic stroke. But current smokers compared with never smokers and past smokers had an age-adjusted relative risk for hemorrhagic stroke of 2.33. The relative risk for ICH was 1.95, and for SAH, 3.61.

The researchers say smoking may damage arterial walls, making arteries more prone to rupture.

Kurth says this study establishes smoking as a risk factor for ICH. Smoking has about the same impact on ICH as it does on ischemic stroke.

“Our results add to the multiple health benefits that can be accrued by abstaining from cigarette smoking,” he says.

Co-authors are Carlos S. Kase, M.D.; Klaus Berger, M.D., MPH, M.Sc.; Elke S. Schaeffner, M.D., M.Sc.; Julie E. Buring, Sc.D; and J. Michael Gaziano, M.D., MPH.

The study was partly funded by the National Cancer Institute and the National Heart, Lung, and Blood Institute.

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