Healthy travel: Don't let this common hazard spoil your best-laid plans

Long trips come with an increased risk of blood clots deep in the leg veins, which can have serious complications.

Vacation getaways, whether to sun-drenched beaches or ski havens, can be rejuvenating. However, the inactivity imposed by hours of sitting in planes, trains, or automobiles can increase the risk of developing blood clots in your legs, a condition called deep-vein thrombosis (DVT), which is increasingly common with age.

In about half the people with DVT, blood clots form silently; the rest develop symptoms. If blood clots grow in place, they can interfere with circulation in your leg, causing pain and swelling. If small pieces of them break off and travel to other parts of your body, they are known as emboli. A pulmonary embolus—a traveling clot that lodges in the lungs—can block oxygen supplies to your body, leading to fatigue, breathlessness, and even death. Approximately 300,000 people die from pulmonary embolism in the United States every year.

A blood clot can also form in a varicose vein, producing a lump in the skin that may be red, warm, and tender. This type of clot, called a superficial thrombus, is not as dangerous as a clot forming in a deep vein because it can't travel to your lungs. However, if a superficial thrombosis seems to be growing or becoming painful, you may want to have it checked by your doctor.

Are you at risk for DVT?

"It usually takes more than a single factor for DVT to develop," says Dr. Julianne Stoughton, a vascular surgeon at Harvard-affiliated Massachusetts General Hospital. The chance of developing a blood clot begins to increase after age 40 and continues to rise throughout life. You are also more likely to develop blood clots if the walls of your veins are injured, you are bedridden or inactive, or you are taking a medication that promotes blood clotting. Certain medical conditions like factor V Leiden mutation (a genetic tendency to form blood clots), cancer, and heart disease also increase risk.

Dr. Stoughton advises using the risk-factor assessment form like the one available on the Centers for Disease Control and Prevention website (cdc.gov/Features/Thrombosis) to see how likely you are to develop DVT. If you have several risk factors, it's a good idea to talk to your doctor, who may choose to perform a physical examination and may order an ultrasound of your leg veins. It's painless and relatively inexpensive, and an ultrasound can identify whether you have clots and need to take measures to prevent the clots from growing or breaking away.

Travel tips to reduce DVT risk

Because sitting for long periods can increase the risk of DVT, people at risk are more likely to develop blood clots during trips that take more than a couple of hours. However, a few preventive measures may help.

• Wear graduated compression stockings. These thigh-high or knee-high stockings are made from an elastic material that exerts a slightly greater pressure around the ankle than around the calf. You should have your first pair fitted by a health professional to make certain you have the right size. And if you envision compression hose as thick, rubbery, and beige, you may be surprised to find that they are now virtually indistinguishable from opaque hose and come in a variety of colors.

• Don't sit still for long periods. Take a break every hour. If you're on a plane, bus, or train, walk the aisles; if you're driving, stop at a rest area. While you are seated, practice tracing the letters of the alphabet in the air with your right foot, using your big toe as a "pen point." Repeat the exercise with your left foot.

• Stay awake. Don't take a sleeping pill. A long nap in a seated position allows your blood to pool in your legs.

• Wear loose clothing. It's less likely to restrict your blood flow.

• Keep hydrated. Drink plenty of water. Avoid alcohol, which is dehydrating. Staying hydrated may mean more bathroom visits, but walks down the aisle keep your blood circulating.

• Talk to your doctor about low-dose aspirin. There is some evidence that it can prevent DVT.