In-Flight Blood Clots: Theory Grounded
Low Oxygen on Long Flights Doesn't Seem to Cause Clots, Study Shows
WebMD News Archive
Checking for Clotting Risk continued...
The study included 12 women who were taking oral contraceptives
(which raise clotting risk) and another group of 12 people aged 50 and older.
Those groups' test results didn't show higher clotting risk, but with such few
participants, it's hard to be sure of that finding, the researchers note.
It's not clear if the results apply to people with other health conditions.
The study was funded in part by the U.K.'s Department for Transport.
Another recent study, done in the Netherlands, showed that low oxygen levels
on long flights might increase clotting risk in some fliers.
The finding that low oxygen and prolonged sitting didn't raise clotting risk
was "surprising," writes editorialist Peter Bartsch, MD. He works in Germany at
the Universitatsklinikum Heidelberg and wasn't involved in Toff's study.
The Dutch and British studies weren't exactly like a real flight, Bartsch
notes, noting the alcohol ban and hourly activity allowed in the
Bartsch writes that "the small number of older participants and individuals
taking oral contraceptives preclude drawing reliable conclusions about these
groups." He also asks if lower oxygen levels might interact with other risk
factors, such as advanced age and a history of DVT.
The results might not apply to clotting risk in mountain climbers at high
altitudes, Bartsch also notes.
Avoiding in-Flight Clots
In a University of Leicester news release, Toff commented on his study.
"Although we found no evidence that the low pressure and low oxygen activate
blood clotting, we know from many other studies that prolonged sitting, such as
during long journeys by air, road or rail, does increase the risk of deep vein
thrombosis (DVT). That link is quite clearly established," Toff says.
"The overall risk of thrombosis [clotting] after a long-haul flight is
estimated to be about 1 in 2,000," he continues. "For people with known risk
factors, the risk may be higher but for those without other risk factors it is
likely to be very low and should be kept in perspective."
Toff recommends taking "sensible precautions" on long flights, such as
regularly doing leg exercises, getting up and walking around the plane's cabin
from time to time, wearing special compression stockings, and (if recommended
by a doctor) taking anticlotting drugs.