Long Flights Double Risk of Blood Clots
Economy Class Syndrome Largely Limited to Older, Overweight People
WebMD News Archive
Dec. 8, 2003 -- Rather than bringing a book on long airplane
trips, you might want to bring your walking shoes.
New research shows that flights over eight hours long can
double the risk of potentially dangerous blood clots during or shortly after
flight. But you can substantially reduce your risk of these complications by
knowing your risk and simply getting up and stretching in flight.
Three studies in the Dec. 8/22 issue of The Archives of
Internal Medicine shed new light on the link between air travel and the
much-hyped "economy class syndrome."
Researchers say air travel mildly increases the risk of blood
clots forming in the veins, known as venous thromboembolism (VTE), but the risk
is greatest in older people, those who are overweight, or have other genetic
and environmental risk factors.
For example, people who lack certain proteins that prevent or
break up clots or women who take birth control pills may be 14 to 16 times more
likely to develop these blood clots during or shortly after air travel.
Assessing the Risk of Economy Class Syndrome
In the first study, Italian researchers compared 210 people who
suffered VTE with 210 similar healthy people.
The study showed that air travel was reported in the preceding
month by 31 of those who had suffered the blood clots compared with 16 of the
More than 100 of those who had VTE also had genetic factors
that predisposed them to blood clots compared with only 26 of the healthy
people. Use of birth control pills was also much more common among women with
VTE (61% vs. 27% of those of reproductive age).
Researchers say that air travel alone was only a minor risk
factor for VTE, but the addition of either clotting risk factors or use of
birth control pills increased the risk of blood clots by 16-fold and 14-fold,
In the second study, German researchers used ultrasound to
detect blood clots in 964 passengers who had just returned from long-haul
fights and more than 1,200 nontraveling people.
Researchers found blood clots in 2.8% of the travelers compared
with 1% of the nontravelers. Most of these did not produce any symptoms and
were found in the calf muscle veins.