Bleeding in the Brain Runs in Families
Jan. 13, 2000 (Urbana, Ill.) -- Close relatives of patients who have
suffered a devastating form of stroke called subarachnoid hemorrhage are three
to five times more likely to fall victim to the same type of stroke than are
members of the general population, although the overall risk of the disease is
still low. That's according to a study reported in the Jan. 15 issue of the
British Medical Journal. The results provide researchers an important
clue that could help them determine which, if any, genes predispose people to
the disorder, experts say.
Subarachnoid hemorrhages (SAH) occur when an aneurysm, an enlarged, weakened
artery, ruptures and patients bleed into the space that covers their brain.
Although they make up only about 5% of strokes, they have a disproportionate
impact, says Daryl Gress, MD, director of the neurovascular service at the
University of California, San Francisco. Unlike ischemic strokes, which tend to
strike older people, SAH tends to strike most often in middle-aged people,
robbing patients of years of life, he says.
And when they hit, they hit hard: 40% of patients die within a month, and
about one-third of the survivors have severe neurological disabilities, says
study co-author David Gaist, MD, PhD, a postdoctoral fellow in epidemiology at
Odense University in Odense, Denmark.
Four earlier studies had shown that parents, full siblings, and children of
SAH patients face an increased risk of the condition, but the studies were
flawed, Gaist says. All of them relied on patients or relatives of patients to
report the occurrence of a subarachnoid hemorrhage in another relative, a
method which can lead to biased reporting and inaccurate estimates, he tells
WebMD. Instead, Gaist and his colleagues investigated Danish national
registries of population and medical records.
"We wanted to see ... if you're related to a person who had this
disease, what is your risk compared to the general population," Gaist
The researchers studied records of over 9,300 patients who were treated for
SAH in Danish hospitals between 1977 and 1995. They then used a national
registry of all the people in Denmark to identify nearly 14,800 children,
siblings, and parents of the patients, and determined whether they had also
experienced stroke from SAH.
The researchers found that first-degree relatives of SAH patients are three
times more likely to develop SAH.
Next, the Danish group hopes to determine why SAH tends to cluster in
families. "We feel fairly convinced that the reason ... is genetic, but we
don't know it," Gaist says.
In addition, the overall incidence of SAH was only 9.25 per 100,000
person-years in the general population. "Increasing that risk three-fold
still makes it pretty uncommon," Gress tells WebMD. "Physicians who
don't deal with this a lot shouldn't make the family feel that they're at high
risk because Grandma had SAH. The added risk isn't that great," he