Air Travel Raises Clot Risks for 2 Weeks

Deep Vein Thrombosis Risk Highest Within 2 Weeks After Long Flight

From the WebMD Archives

Nov. 4, 2003 -- A person's risk of developing a potentially deadly blood clot caused by sitting in an airline seat too long can be four times higher within two weeks after taking a long international flight.

A new study shows the likelihood of developing deep vein thrombosis, a condition also known as "economy class syndrome," drops significantly two weeks after a long-haul flight, which is shorter than the current two- to four-week post-flight "hazard period" suggested by previous studies.

Deep vein thrombosis occurs when blood clots develop in the deep veins of the leg and can happen at any time when the blood can't move through the vessels properly, such as after sitting in a airline seat for hours at a time without moving.

These blood clots can travel through the bloodstream and lodge in the lungs, blocking blood flow and leading to severe organ damage or even death.

Long Flights Raise Clot Risks

In this study, published in the Nov. 8 issue of the British Medical Journal, researchers found the risk of death from flight-related deep vein thrombosis was very small, with about one death reported per 2 million passengers who arrived in Australia on international flights. They say this risk is small compared with the risk of death from motor vehicle crashes or injuries at work.

Researchers studied the health records of 5,408 patients who were admitted to Australian hospitals for deep vein thrombosis and found 46 Australian citizens and 200 foreigners developed the condition within two weeks after arrival on a long flight.

The study showed that the risk of developing the condition was four times higher during this two-week period, and 76% of these cases were attributable to the preceding flight.

Researchers say the fact that more foreigners suffered from the condition may be the result of longer flight times, which increases the risk of deep vein thrombosis, and also a so-called "healthy traveler" effect among the Australians, which suggests that people who travel internationally often are healthier and less likely to develop deep vein thrombosis than those who do not travel.

The study also showed that the risk of deep vein thrombosis rises by 12% each year if a long-haul flight is taken annually.

Advice for People at Risk

But researchers say a person's individual risk of suffering from a clot might higher if they have certain medical conditions that increase the risk of clots, such as:

In addition, smokers, pregnant women, overweight individuals, the elderly, and tall people may also have a higher risk of flight-related deep vein thrombosis.

Researchers say that although the average risk of deep vein thrombosis is small, airlines and health authorities should continue to advise passengers on ways they can minimize their risk, including:

  • Getting up and walking around the plane during long flights
  • Stretching the legs and ankles when seated
  • Drinking plenty of water in flight

Show Sources

SOURCES: Kelman, C. British Medical Journal, Nov. 8, 2003; vol 327: pp 1072-1075. WebMD Medical News: "A Possible Reason to Fly First Class: 'Economy Class Syndrome.'"

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