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Family History Raises Odds Of Stroke At Young Age

DALLAS, TX -- April 25, 2003 -- Family history was found to be a significant risk factor for two common types of stroke, British researchers report in today's rapid access issue of Stroke: Journal of the American Heart Association.

"Traditional risk factors for stroke, such as high blood pressure, smoking, diabetes and high cholesterol, only explain about half of all stroke risk," says Paula Jerrard-Dunne, M.D., a clinical research fellow working with Hugh S. Markus, M.D. at St. George's Hospital Medical School in London. "There is growing interest in the role of genetic risk factors for stroke."

Previous studies found conflicting results about the association between family history and stroke, perhaps because they usually lumped all types of strokes together, rather than evaluating the different disease processes separately, Jerrard-Dunne says.

In this study, researchers sought to determine the impact of family history on different types of ischemic strokes. Ischemic stroke, the most common type of stroke, is caused by a blood clot that obstructs blood flow to the brain. A common cause is a build-up of cholesterol-like material that narrows the large arteries in the neck (carotid arteries). This is called "large-vessel disease."

Ischemic strokes also can occur when small blood vessels in the brain are blocked. Known as small-vessel or lacunar strokes, they are closely associated with high blood pressure. Small-vessel strokes are usually less severe than large-vessel strokes but can nonetheless damage brain tissue. Small vessel disease is a major source of dementia.

The study involved 1,000 Caucasian patients (average age about 65) with ischemic stroke. They were compared with 800 stroke-free individuals who were matched for age and sex. Family history of heart attack and stroke was determined by interviews, and researchers documented conventional stroke risk factors, such as age, gender, smoking status, blood pressure, diabetes, cholesterol abnormalities and coronary heart disease. Complete data, including family history, were available for 944 stroke patients and 789 controls.

All of the stroke patients were evaluated by a neurologist, who determined the type of stroke they'd had.

Researchers found that a family history of vascular disease at age 65 or younger is an independent risk factor for both large-vessel and small-vessel stroke.

Compared to controls, stroke patients who had large-vessel strokes were more than twice as likely (2.24 odds ratio) to have an immediate family member who had suffered stroke at age 65 or younger or a family member who had a heart attack. The odds ratio was 1.93 for small-vessel stroke patients with this family history compared to controls.

When the analysis was limited to stroke patients age 65 and younger, the significance of family history increased.

Participants with large-vessel strokes were almost three times as likely (2.93 odds ratio) as controls to have an immediate family member who had suffered stroke at age 65 or younger or a family member who had a heart attack. Those with small-vessel stroke were more than three times as likely (3.15 odds ratio) to have this family history compared to the controls.

The findings suggest that studies investigating the genetic basis of ischemic stroke that focus on specific subtypes in younger age groups may be more effective, the authors say.

The research team has begun analyzing DNA samples of patients with large- and small-vessel disease to try to find genes that predispose people to those two types of strokes. Identifying the genes might lead to a better understanding of the disease processes involved in different types of stroke, Jerrard-Dunne says. Future development of gene therapies for stroke might have a better chance of success if studies focus on selected patient groups in whom genetic factors are most important, she notes.


SOURCE: American Heart Association

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