MONDAY, Aug. 8 (HealthDay News) -- People who have two or more
siblings who have suffered blood clots in deep veins such as those
in the legs and pelvis -- a disease known as venous thromboembolism
(VTE) -- have a relative risk 50 times higher for developing such
clots themselves, Swedish researchers report.
Individuals with only one sibling with VTE are two times as
likely to suffer the dangerous blood clots.
This is the first study in a large population to show that the
risk for VTE runs in families, the researchers say. VTE causes
blood clots called deep vein thrombosis, which, if they break
loose, can travel to the heart, lungs or brain and, if untreated,
tend to be fatal.
"We found genetic factors are important in the risk for VTE," said lead researcher Dr. Bengt Zoller, an associate professor, at the Center for Primary Health Care Research at Lund University in Malmo.
"A sibling history of VTE is an important risk factor for VTE," he said. However, Zoller pointed out that most people who develop a VTE don't have a family history of the condition.
While the relative risk is very high, the absolute risk is much
lower. In the general population, the absolute risk for VTE is 3 in
10,000 each year and for those whose family history puts them at
high risk it is 15 in 10,000, each year, Zoller said.
The report is published in the Aug. 8 online edition and the
Aug. 30 print issue of
For the study, Zoller's team collected data on 45,362 people who
were hospitalized with VTE. Among these people, 2,393 had a brother
or sister who also had a history of the condition.
The researchers found that for those aged 10 to 19 years, there
was a five times greater risk of VTE if they had a sibling who had
had a VTE, compared with those who didn't have this family history.
For older patients, those 60 to 69, the risk was twice as high.
Taking into account age differences between siblings, Zoller's
group determined that no environmental factor played a role in the
increased risk of VTE.
In addition, while VTE was found in both men and women, the rate
was higher among women, especially those 10 to 40 years old. After
50, however, the risk was higher in men than women, the researchers
Risk factors for VTE include surgery, heart failure, smoking,
obesity, cancer, long periods of inactivity (such as when driving
or flying), sitting or lying in bed, fractures in the legs or hip
and taking birth control pills.
Modifying these risk factors can lower your risk for VTE, Zoller
said. After heart attack and stroke, VTE is the most common
cardiovascular illness and affects one in 1,000 people each year,
the researchers said.
Commenting on the study, Dr. Jack Ansell, chairman of the
department of medicine at Lenox Hill Hospital in New York City,
said that "the study confirms a lot of what we know, but it also
provides impetus to greater investigation of genetic and
However, Ansell noted that genetics is not the whole story.
"There are many individuals with inherited predisposition that
never have a problem, so it's not an all or none phenomenon," he
Conversely, if you don't have a family history of VTE, that
doesn't mean that you will not have one, Ansell said. "There are
clearly people who have no risk for a VTE who end up with an event
due to acquired factors like an accident or cancer," he said.
This study should not cause people to panic, as the risk for
having a VTE is low regardless of family history, Ansell said.
However, he added that people with a family history of VTE
should let their doctor know before undergoing any surgery. This
will allow the doctor to take preventive measures to prevent the
risk of clotting.
For more information on deep vein thrombosis, visit the
U.S. National Library of Medicine.