The most common type of stroke is ischemic stroke, which results from an artery blockage that prevents blood from reaching part of the brain. Hemorrhagic strokes are less common, accounting for 10 percent to 20 percent of all strokes.
Subarachnoid hemorrhage (SAH), which accounts for about 7 percent of strokes, occurs on the surface of the brain and usually results from a ruptured intracranial aneurysm, a blood vessel in the brain that suddenly bursts.
“These are not subtle strokes,” says Brett M. Kissela, M.D., lead author of one of the papers and an assistant professor of neurology at the University of Cincinnati in Ohio. “They are usually painful and generally quite devastating and nearly 40 percent of the people who get them die within 30 days.
“These strokes generally happen in young people, which means they die at an early age or lose decades of useful life because they are unable to work,” Kissela says.
The study included 107 individuals with SAH and 197 without stroke who were participants in the Genetic and Environmental Risk Factors and Hemorrhagic Stroke Study, conducted by the University of Cincinnati College of Medicine. Participants came from Ohio and Kentucky hospitals within a 50-mile radius of the medical school.
Heavy alcohol users had more than a 10-fold increased risk of SAH compared to non-drinkers. Other important factors included hypertension (high blood pressure), smoking and having a relative with SAH.
Previous studies have yielded conflicting findings regarding the role of hypertension in SAH. However, Kissela and his colleagues found a strong association between the two.
“The increased risk with a family history implies that genetic factors may be associated with subarachnoid hemorrhage,” Kissela says. Researchers from the same group conducted a second analysis of people who had suffered an intracerebral hemorrhage (ICH), a type of hemorrhagic stroke that occurs when an artery inside the brain ruptures. Intracerebral hemorrhages account for about 10 percent of strokes.
Daniel Woo, M.D., assistant professor of neurology at the University of Cincinnati College of Medicine, led this study, which included 188 ICH patients and 366 healthy people from the same area who had not had a stroke. Patients and controls were matched by gender, race and approximate age.
ICH takes two forms: Lobar strokes occur deep in the brain and nonlobar strokes affect the lobes, where thinking and cognition take place. Woo and his colleagues found the risk factors for each type were different.
By comparing the control and stroke groups, the researchers determined that the major risk factors for ICH were: having a first-degree relative (parent, sibling, or child) who had suffered an ICH; frequent alcohol use (more than 2 drinks per day); and hypertension. A higher level of education was associated with a lower risk.
A family history of ICH or a previous stroke increased the risks for both lobar and nonlobar ICH. Frequent alcohol use, but not hypertension, heightened the danger of a lobar stroke. Hypertension, but not alcohol consumption, raised the odds of suffering a nonlobar stroke.
The researchers also sought to determine whether variations of genes that are involved in cholesterol metabolism, called apoE2 and apoE4, increased the risk of ICH. Variants of these genes have been associated with stroke, heart disease and Alzheimer’s disease.
The new study found, to the researchers’ surprise, that the gene variants increased the risk for lobar stroke but not nonlobar hemorrhage. “We estimate that about 30 percent of all lobar hemorrhages are attributable to a genetic risk factor,” says Woo.
So the conclusion is that genetics play a role in hemorrhagic strokes, but these strokes may be preventable by treating hypertension and reducing risk factors such as frequent alcohol use, he says.
“We can’t control our genetic make up, but there are ways to get physicians and patients focused on reducing the risk factors they can control, because this kind of stroke is largely preventable,” says Woo.
Co-authors with Dr. Woo and Dr. Kissela on both papers are Laura R. Sauerbeck, R.N.; Jane C. Khoury, M.S.; Janice Carrozzella, R.N.; Arthur M. Pancioli, M.D.; Edward C. Jauch, M.D. Charles J. Moomaw, Ph.D.; Rakesh Shukla, Ph.D.; James Gebel, M.D.; Robert N. Fontaine, Ph.D.; and Joseph P. Broderick, M.D. Additional co-authors with Dr. Woo are Jerzy P. Szaflarski, M.D.; Anil G. Menon, Ph.D.; and Ranjan Deka, Ph.D.
NR02 – 1071 (Stroke/Woo-Kissela)
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Stroke