Twenty-something-year-old Emma Christofferson landed at Heathrow airport in London after a 20-hour flight from Sydney, Australia. During the last leg of the flight, she complained of feeling sick. Minutes after landing, she walked off the plane, collapsed, and died before ever reaching a hospital. Her death was attributed to a pulmonary embolism (blood clot in the lungs) resulting from deep vein thrombosis (DVT).

Ms. Christofferson's age and health status did not fit the usual profile of a person at risk for developing DVT. Her tragic, untimely death attracted worldwide media attention, and spotlighted a question that doctors have been debating for years: are long distance travelers at greater risk of developing DVT?

What Is DVT?

DVT (also known as thrombophlebitis or venous thromboembolism) occurs when a blood clot develops in the deep veins of the legs and groin (the lower-abdomen/upper thigh areas). These deep veins are not visible at the skin's surface, and are not related to varicose veins . A clot that breaks loose and travels through the deep veins to the heart and lungs can cause severe blockage of blood flow or death.

Symptoms, Diagnosis, and Treatment

People who develop DVT don't always have symptoms. However, those who do usually experience the following symptoms in one leg or the other (rarely both):

Symptoms of DVT include:

  • Redness and/or warmth of the skin
  • Pain in the calf or behind the knee
  • Swelling of the foot and/or lower leg

Sudden, severe shortness of breath, with or without chest pain, may signal that a clot has embolized (traveled) to the lungs.

DVT can be diagnosed by ultrasound imaging tests , which highlight blood flow in the veins and show clot formation. If a clot is found, blood-thinning medication to stabilize the clot and allow it to dissolve will be prescribed immediately. Hospitalization may be required for several days for treatment and observation, and patients often take oral medication for several months afterwards, to ensure restoration of normal blood flow through the vein.

Risk Factors

It is estimated that two million people in the United States develop DVT annually. Risk factors include:

  • Recent surgery or injury, especially in the hip, leg, or knee
  • Smoking
  • Older age
  • Obesity
  • Pregnancy
  • Use of oral contraceptives, especially in smokers
  • Cancer
  • Previous history of a blood clot

Travel and DVT

The connection between DVT and immobility was first noticed in 1940 during World War II, when physician Keith Simpson reported seeing an increased incidence of pulmonary embolism in people who sat still for long hours in London air raid shelters.

Today, we are sitting still for a very different reason: travel. More people than ever are traveling farther and more frequently in cramped cars, buses, trains, and planes. This initially prompted the nickname "economy class syndrome" for travel-related DVT.

Although there is significant anecdotal evidence linking DVT to long distance travel, results from scientific studies have been sparse and contradictory; the overall consensus is that more research is necessary. Two case control studies (published in the British Medical Journal and Chest ) examining air travel and DVT arrived at opposing conclusions. Whatever the degree of risk, most health professionals agree that taking preventive measures against DVT during long distance travel is a good idea.

One cautionary note: DVT may surface after travel has been completed. If you experience any of the symptoms listed above, contact your doctor immediately.

Preventing DVT While Traveling

If you are planning any kind of travel that requires sitting for long stretches of time, be sure to do the following:

  • Get up and walk around as much as possible—at least once an hour, if possible. Stand up and stretch your arms and legs in your seat if there is no room to walk.
  • Do in-seat calf exercises and heel/toe lifts frequently to keep the blood circulating. Also massage the feet, ankles, calf muscles, and lower legs.
  • Try to sit comfortably and avoid crossing your legs.
  • Arrange optimal seating: try to sit in an area that affords you some space, such as an aisle, exit row, or bulkhead seat.
  • Stay hydrated, drink plenty of fluids, but avoid drinks that contain alcohol or caffeine, as they promote dehydration.
  • Avoid smoking; this is especially important if you are taking oral contraceptives.
  • Wear loose clothing and avoid tight clothing that restricts blood flow (eg, tight waistbands).
  • Wear good hosiery. Avoid socks or stockings that bind tightly around the ankles or below the knees. People with poor venous circulation (severe varicose veins and/or chronic swelling of the feet) may want to purchase compression stockings, which help prevent blood from pooling in the leg veins.
  • If you are at high risk for developing DVT, your doctor may prescribe low molecular weight heparin, a medication that prevents clotting. Low-dose aspirin is sometimes recommended, but there is disagreement among physicians regarding its efficacy in preventing DVT. Check with your own physician regarding your current health and medication use.