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Deep Vein Thombosis -- Risk Factors

When Blood Slows, Clot Formation Rises, Potentially Triggering DVT

Oct 7, 2008 Steve Vogel

Air travel is a significant risk factor, especially for endurance athletes with low heart rates and low blood flow to the legs.

Deep vein thrombosis, or DVT, is sometimes called the “stealth disease” because it happens without victims knowing it. Over several days or more, usually after a long plane flight, a blood clot can form in the leg, or even the arm, without any symptoms.

The risk of a ‘stealth’ clot forming in the calf? A piece of it might break off and move through the veins to the lung, where it could get lodged in an artery, and cause pain, fainting and even death.

More typically, people with a DVT experience some kind of swelling and/or pain in their calf, and sometimes see dark swelling behind the knee. Even so, these symptoms often go misdiagnosed by physicians. So it’s important for people to understand what the risk factors are -- before it's too late.

DVT Risk Factors

• Long airplane flights. This is the biggest risk factor for DVT. About 3-5 percent of air travelers develop clots, according to Airhealth.org. The longer the flight, the greater the risk. However, some studies show there are many cases that develop after relatively short flights of three hours or so.

• Athletic training for endurance sports. Marathoners and triatheletes are especially at risk, although the vast majority of DVTs result from these athletes taking long distance flights. Airhealth.org reports that about 85 percent of air travel thrombosis victims are athletic. Why? Because a slow heart rate – regarded as a benefit from endurance training – presents a greater risk of stagnant blood in the legs and, in turn, clotting activity. In addition, common bruising and sore muscles can trigger a clot.

• Recent surgery or injury. Again, athletes like marathoners, kick-boxers and martial artists can have leg injuries, in which the body forms clots in the vein to protect against internal bleeding. It's advisable to avoid surgery of the calf for at least 30 days after air travel. At the very least, talk to a doctor first to assess the risk.

• Personal or family history of DVT can contribute to the formation of clots. In the last five years, mutant coagulation genes have been identified in family gene pools.

• Cancer can change the coagulation properties in the blood. Cancer patients are four times more likely than the non-cancerous population to develop a DVT, according to Venous Thromoembolism and Cancer: Risks and Outcomes, 2003.

• Obesity, pregnancy, or women taking estrogen as birth control have all been cited as potential risk factors.

• Post age-40. Yes older folks are typically at higher risk, but people of all ages can develop DVT. Airhealth.org says 83% of DVT victims are under age 40.