DALLAS (American Heart Association) -- A stroke that's deadly up to 50 percent of the time can be largely prevented, according to a report in the rapid access issue of Stroke: Journal of the American Heart Association.

The study indicates that subarachnoid hemorrhage (SAH) is largely preventable among younger adult populations by using high blood pressure drugs and with behavioral changes such as quitting smoking and cocaine use, says Joseph P. Broderick, M.D., the study's lead author and a professor of neurology at the University of Cincinnati in Ohio.

"Our results should give people - especially those with a family history of bleeding stroke - even more impetus to take better care of themselves," he says.

Unlike other types of stroke that occur more often in the elderly, SAH often occurs in younger populations, Broderick says. SAH occurs when a blood vessel on the surface of the brain ruptures and bleeds primarily into the space surrounding the brain. While SAH represents only about 3 percent of all strokes, it is among the most deadly, with a 39 percent to 50 percent death rate.

To look at what might be causing these strokes among young and middle-aged adults, researchers identified patients with SAH from 44 hospitals in Connecticut, Massachusetts, Ohio, Kentucky, Rhode Island and Texas between 1994 - 99. The 312 patients participating in the study were men and women between ages 18 and 49 with no prior stroke. They answered questions about lifestyle and other factors that could be related to the development of SAH. Researchers then compared the data from the stroke patients with that of 618 matched controls who had not had a stroke.

Researchers found notable differences between the two groups.

"One of the study's key findings is that two-thirds of the people who had a subarachnoid hemorrhage in this age group were current cigarette smokers. That is a huge number," Broderick says. "If you're a smoker in this age group, you are about 3.7 times more likely to have this type of stroke than if you're not a smoker."

This is the first study to scientifically prove that cocaine use is associated with an increased risk of subarachnoid hemorrhage, Broderick says. While only 3 percent of people with SAH reported recent cocaine use, none of the people in the control group reported using it.

High blood pressure is another factor the study identified with higher risk of SAH, highlighting the importance of monitoring blood pressure and controlling it if it's high, Broderick says. Stroke patients in the study were more than twice as likely to have high blood pressure as controls.

"There is also a familial tendency for this type of stroke," he says. People in the study who had SAH were about 3.8 times more likely than controls to have a family member who had had bleeding stroke.

Researchers also found that, compared with heavier people, those with lower body mass index (relatively thinner) were about 1.5 times more likely to suffer a bleeding stroke. "Quite frankly, we don't understand that association very well," Broderick says. "The other things that appeared to increase stroke risk a little were caffeine and nicotine in pharmaceutical products. These may be independent factors but need to be explored more - the risk associations are not as clear."