When Flying, Travelers Should Watch for Dangerous Blood Clots by Gina Shaw When 28-year-old Emma Christofferson collapsed at Londonís Heathrow Airport after a long-haul Qantas flight from Australia in October 2000, and later died, it was the first time most people had heard of a travel hazard known as deep vein thrombosis (DVT). People used to call it ìeconomy class syndrome,î but in the years since Christoffersonís death, it has become clear that this blood clotting disorder is an equal-opportunity threat, attacking long-haul travelers in first class and coach alike. Sitting in one position for a long time, without moving your legs, can cause blood to pool in the lower legs, leading to clots in the deep veins of the legs. These clotsódeep venous thrombosisócan lead to more than just swelling and discomfort. If a piece of the clot breaks off and travels to the lungs, it can result in a potentially fatal pulmonary embolism. Even if your body is able to dissolve the clot on its own, the vein can become permanently damaged in the meantime. The problem isnít where in the plane you sit, but how long you stay there. A quick hop from Atlanta to New York may not be a problem, but how about that 11-hour flight from London to Tokyo? Most travelersóespecially business travelersósettle in with their books, papers and laptops, and try to pass the time by working or napping, not moving around. And although planes arenít the only places where people sit in one place for a long time, airline passengers also face the added risk factors of low air pressure (remember how your shoes are always tighter when you get off the plane?) and dehydration, making DVT more likely. A New Zealand study, published in the Lancet last December, found that long-distance fliers (people who flew at least 10 hours for no less than four hours at a stretch over the course of a six-week period) faced a 1 percent risk of developing symptoms of DVT. The risk may actually be much higheróother studies have found that as many as one in 10 long-haul fliers could have ìsymptomlessî DVT. According to the Society of Interventional Radiology, 600,000 new cases of DVT are diagnosed every year in the United States alone. Certain factors put some people at an even higher risk of DVT when they travel, said Dr. Thomas Wakefield, a vascular surgeon with the University of Michigan Health System. ìPerhaps the most important risk factor is age. We know as we age that our chances of developing deep venous thrombosis significantly increase,î he said. ìThere is also mounting evidence that obesity, in and of itself, is a risk factor for the development of deep venous thrombosis.î Pregnant women and smokers also face added DVT risk. But this doesnít mean that healthy, athletic, young nonsmokers can ignore the risk of DVT. In fact, DVT activist Michael Reynolds, who suffered a pulmonary embolism in Paris in October of 2000, has compiled information suggesting that athletesóespecially endurance athletesómay be at particular risk for air travel-induced DVT. ìThe biggest risk factor in a jetliner, accounting for a large majority of victims, is athletic conditioning, particularly training for endurance-type, sports-like marathons,î Reynolds noted on his Web site, www.airhealth.org. ìIf you have just run a marathon, you probably have at least minor bruising that can trigger clotting. Kick-boxing also produces such injuries.î If you fly long distances on a regular basis, preventing DVT should be a part of your travel agenda, just like keeping your passport updated. What can you do? Book an aisle seat in an exit row or near the bulkhead if you can. This both increases your leg room, so that you can stretch while in your seat, and gives you easier access to the aisle so that you can move around periodically. Annoy your neighbor. Everyone gets impatient with the fellow traveler who gets up and squeezes past us to go to the bathroom every hour on the hour, but would you rather have an aggravated seatmate or a blood clot in your leg? Just because youíre seated next to the window doesnít mean that you shouldnít get up now and then. Pay attention to those exercise videos the airlines have begun showing about DVTóthey actually do help reduce the risk of clotting, according to Wakefield. For example, you can clench and unclench your toes to exercise calf muscles and stimulate blood circulation. Flexing your ankles also frequently helps. Watch what you drink. Dehydration can contribute to DVT risk, so opt for water and other alcohol-free, caffeine-free drinks when the beverage cart comes around (and skip the salted nuts). Finally, wear loose, unconstricted clothing and avoid socks that bind below your knees. Air Health also offers a printable wallet-size card (www.airhealth.org/leaflet.html) in English, French and Spanish with DVT prevention tips and symptoms to watch for. Gina Shaw is the medical writer for The Washington Diplomat.