Quick, what is the the fifth leading cause of death in the United States? Heart problems? Liver failure? Cancer?

You probably won't believe me when I tell you it is flying in airplanes. Deep Vein Thrombosis in air travelers is far more frequent than most of us know. Deep vein thrombosis (DVT) is a dangerous condition where lack of movement can cause clots to form in the veins of the legs. If the clot breaks off and travels to the heart or lungs, it is often lethal. In 2001 "The Lancet" published an analysis estimating that 1 million cases of DVT related to air travel occur in the US every year and that 100,000 of these cases result in death (Lancet, September 8, 2001, p. 838).

According to a study in the New England Journal of Medicine, the risk increases with distance traveled. LINK The risk can be sharply reduced on long haul flights by wearing compression stockings. However many people wear them incorrectly LINK. It seems the thigh-high stockings may be more uncomfortable than the knee-length ones, so perhaps try the knee-length ones first. They seem to be just as effective.

Researchers in the Netherlands (LINK) found that siting in the window seat raises the risk of DVT, by 200% compared to the aisle seat or middle seat. This study found that compression stockings did NOT prevent DVT, which stands out from other results.

Although age is a risk factor, young, athletic people are not free from risk, in fact DVT may be one of the most important causes of death in the 20-44 year age bracket, according to airhealth.org. And althought DVT is often called "Economy Class Syndrome," Business-class and First Class passengers are also at risk, unless they keep moving or wear compression stockings [International Travel News 30.1 (March 2005): p96(2)]