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More Risks for Leg Blood Clots

Low Oxygen May Be Another Risk for Some on Long Flights
WebMD Health News
Reviewed by Louise Chang, MD

March 9, 2006 -- For some people on long flights, sitting still for hours might not be their only in-flight risk of developing leg clots.

In The Lancet, researchers in the Netherlands found that some people were at higher risk for leg clots on a long flight than on land. But immobility -- a risk factor for leg clots -- didn't seem to be the only reason for that, the study shows.

Low oxygen levels on planes might be a reason, but that's not certain, write the researchers. They included Anja Schreijer, MD, of the vascular medicine department at Leiden University in the Netherlands.

Schreijer's team isn't recommending that anyone avoid long flights. No one in their study developed leg clots, regardless of their risk factors.

About the Clots

Schreijer's team studied risk of deep vein thrombosis (DVT), a potentially dangerous type of blood clot that develops in the deep veins of the legs, torso, or arms.

Such clots can grow, break off, and travel through the bloodstream to the lungs, causing a life-threatening condition called pulmonary embolism.

DVT risk rises if people are seated for a long time. That's why travelers are encouraged to move around every now and then on long flights. People are at risk for DVT in lower extremities during periods of immobility. Walking causes contraction of leg muscles, which gets the blood in the veins moving and thus helps prevent clot formation. Compression stockingsCompression stockings for your legs have also been shown to cut in-flight clot risk.

Of course, DVT isn't limited to air travelers, and it's not just due to immobility. DVT can be caused by conditions that slow blood flow or thicken blood. It is also associated with injury, pregnancy, use of hormones (such as estrogen or birth control pills), genetic disorders, damaged valves in veins, and cancer.

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