Deep vein thrombosis

Sitting in cramped seats for hours on end is uncomfortable, but it can also put your health at risk. Deep vein thrombosis (DVT) is a condition that can occur as a result of slow or minimal blood flow, usually to the legs. Long periods of immobility, such as sitting on a long-haul flight or road trip, can increase your risk.

Deep Vein Thrombosis and Pulmonary Embolism

DVT is a condition where blood clots develop in the deep veins, usually in the legs. These clots can cause localized pain, redness, swelling, and be warm to the touch but you may not have any symptoms. DVT becomes dangerous when a piece of clot breaks off and travels to the lungs, causing a Pulmonary Embolism (PE) which can be life-threatening.

Pulmonary Embolism symptoms include sudden shortness of breath, rapid heart rate, chest pain, and light-headedness or fainting. This is different than a stroke or heart attack which occur when blood clots block the arteries. When you suffer from both DVT and a Pulmonary Embolism it’s known as Venous Thromboembolism (VTE).

Understanding the risk

Air travel is what many people associate with DVT but any period of prolonged sitting (over 4 hours) can increase the risk of blood clots. This includes travelling by car, train, or bus or even sitting at a desk for long periods of time.

Many different factors contribute to increased risk of DVT but being immobile for a long period of time (especially if it cuts off circulation to your legs) is probably the most important. Other risk factors include obesity, smoking, height (being very tall or very short), pregnancy, taking hormones such as birth control pills or hormone replacement therapy, being over 40 years of age, varicose veins, previous incidence of DVT or Pulmonary Embolism, cancer, recent surgery, and a genetic predisposition to blood-clotting problems.

How to reduce the risk

You can reduce the risk of DVT by limiting the amount of time you spend sitting. Here’s what you can do:

When booking your flight, choose an aisle seat so you have the freedom to stand up, stretch your legs, and walk around. If you can’t get an aisle seat, don’t be shy about asking your seatmate to get up.
Avoid taking sedatives during flights to decrease the likelihood of prolonged sleep. If needed, set an alarm to remind you to get up and stretch every few hours.
Wear comfortable, loose fitting clothing.
Don’t stow any luggage underneath the seats in front of you so that you can move and stretch your legs.
Avoid dehydration: Drink water and don’t consume alcohol.
Walk around the cabin for a few minutes every hour to get the blood moving in your legs. If you have time before your flight, take a walk around the terminal.
Calf muscle exercises like foot pumps are also helpful. While sitting, point your toes down to the floor and raise your heels, then do the opposite and point your toes toward the ceiling with your heels on the floor. Repeat several times. Learn more about in-flight exercises here.
If you are at higher risk of getting DVT, talk to your doctor before your trip. You may want to get graduated compression stockings or may be prescribed an anticoagulant if you have a history of DVT. Note that taking Aspirin does not prevent DVT.
If you suspect DVT or PE, seek medical assistance immediately. It’s an emergency.

More information

Pulmonary Embolism and Deep Vein Thrombosis, by Samuel Z. Goldhaber, MD; Ruth B. Morrison, RN, BSN, CVN.
WHO Research Into Global Hazards of Travel (WRIGHT) Project
Preliminary Evaluation of Recommended Airline Exercises for Optimal Calf Muscle Pump Activity, by K.J. O’Donovan, T. Bajd, P.A. Grace, D.T. O’Keeffe, G.M. Lyons.
Immobility, circulatory problems and deep vein thrombosis (DVT)

Last reviewed and updated: December 11, 2020.

General Resources

General Resources

Deep vein thrombosis