The Journal: Lancet

The Study: An eight-hour chartered Boeing flight, an eight-hour movie marathon and a day of regular activity? Sounds more like a jet-setter’s fabulous weekend than serious research. But that’s exactly what Dutch researchers asked a group of 71 volunteers (56 women and 15 men) to do in order to investigate whether long-distance air travel can trigger deep vein thrombosis, a condition in which potentially fatal blood clots form in the deep veins of the legs, thighs or pelvis.

What they found is that the combination of a low-pressure and low-oxygen environment of a jetliner with immobilization may contribute more to blood clot formation than long bouts of immobilization on the ground.

The investigators took blood samples from the study participants three times during each day of air travel, sedentary movie-watching or regular activity. Each test day of activity was separated by at least two weeks. The blood tests revealed that, on average, the participants had significantly elevated levels of a particular clotting compound after the long-haul flight but not after the movies or a day of regular activities. The concentrations of the compound were even more pronounced in 40% of the participants, who were already at increased risk of thrombosis due to the presence of a particular gene or the use of contraceptives.

What it Means: There may be something special about long-distance airplane flights—as opposed to long trips by bus or train. What can you do on a plane to reduce your risk of DVT? Remember to contract the muscles in your legs every now and then—walk around or do in-seat calf-raises.

From the Archives:
04/15/2002 Is There a Doctor Onboard?
11/06/00 Dangerous Seats?