Blood Clots and Long-Distance Travel: Advising Patients

Lisa Richardson, MD, MPH


December 16, 2013

Editorial Collaboration

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Hello. I am Dr. Lisa Richardson, Director for the Division of Blood Disorders at the Centers for Disease Control and Prevention (CDC). I am pleased to speak as part of the CDC Expert Video Commentary Series on Medscape. Today I would like to talk about the risks associated with venous thromboembolism (VTE) for long-distance travelers and discuss how you can counsel patients on reducing their risks.

In 2013, CDC published a revised edition of the CDC Health Information for International Travel, also known as CDC's Yellow Book. The chapter on blood clots and travel highlights new recommendations from the American College of Chest Physicians.

An association between VTE and air travel was first reported in the early 1950s. Since then, long-distance travel, defined as travel for more than 4 hours by air, car, train, or ship, has become more common, leading to increased concerns about blood clots and travel. We now know that more than 300 million people who take flights lasting longer than 4 hours are at risk each year.

VTE is a serious public health concern affecting at least half a million Americans each year, and at least 1 in 10 will die suddenly without being diagnosed. Here is what we know about VTE occurrence: In the general population, there will be 1-2 cases of VTE per 1000 people. However, for long-distance travelers, this risk increases 2- to 4-fold, depending on the duration of travel and preexisting risk factors. Also, the more risk factors a person has, the greater the risk for a blood clot developing during or shortly after long-distance travel.

General risk factors include the following:

Older age (increasing risk after age 40 years);

Obesity (body mass index > 30 kg/m2);

Recent surgery, hospitalization, or trauma;

A previous blood clot;

Estrogen use, including hormonal contraceptives or postmenopausal hormone replacement therapy;

Pregnancy and the postpartum period;

Thrombophilia (such as factor V Leiden mutation or antiphospholipid syndrome), or a family history of blood clots;

Active cancer or cancer treatment;

A serious medical illness (such as congestive heart failure or inflammatory bowel disease);

Limited mobility; and

A central venous catheter.

As a clinician, you can counsel your patients on their individual risk for blood clots before they depart on long-distance travel. Asking about family history is a good starting point. Ask whether they or family members have had a blood clot, or whether there are known inherited disorders in the family, such as antithrombin deficiency. Let patients know that the more risk factors they have, the greater their risk of developing a blood clot.

You should also let your patients know how to recognize the signs and symptoms of blood clots. Signs and symptoms of deep vein thrombosis include pain or tenderness in the extremities, swelling, and increased warmth of the affected area, and redness or discoloration of the overlying skin. The most common symptoms of a pulmonary embolism include unexplained shortness of breath, chest pain that can spread to the shoulder and neck, coughing, or fainting.

I encourage all clinicians to become familiar with the prevention measures appropriate for each patient, because prevention is not a one-size-fits-all approach. General measures recommended for long-distance travelers include calf exercises and frequent movement during travel. If you have travelers who have multiple risk factors, you can also prescribe properly fitted, below-the-knee, graduated compression stockings for use during long-distance travel. However, compression stockings are not recommended for travelers who have no risk factors. Medications to prevent clots are recommended only when the potential benefits outweigh the risks.

For patients who have a long-distance trip planned, talk with them about things they can do to prevent blood clots, such as frequent movement during travel. If your patients have no identified risk factors, they should drink plenty of fluids, move about as much as they can, and perform the exercises mentioned above. For patients who have risk factors, compression stockings may be prescribed. By educating patients about their risk of developing blood clots, we can empower them to take steps to prevent this from happening. It is important to increase patients' awareness, because blood clots may be preventable.

Even though the risk of developing a blood clot as a result of long-distance travel is low, please encourage your patients who are planning a long-distance trip to protect their health by taking preventive measures and becoming aware of the signs and symptoms of blood clots. If they suspect that they have a clot, they should seek medical attention right away.

Web Resources

CDC Division of Blood Disorders homepage

CDC Yellow Book: chapter on VTE and travel

2012 American College of Chest Physicians Clinical Practice Guidelines

Lisa Richardson, MD, MPH, is a medical officer at the Centers for Disease Control and Prevention in Atlanta, Georgia, where she serves as the Director of the Division of Blood Disorders at the National Center on Birth Defects and Developmental Disabilities. As Director, Dr. Richardson leads a team of professionals who strive to promote health and improve quality of life for people at risk for or affected by nonmalignant blood disorders, including bleeding and clotting disorders and hemoglobinopathies.

Dr. Richardson is board certified in hematology/oncology, a Robert Wood Johnson Clinical Scholar, and a member of the Alpha Omega Alpha Medical Honor Society. She continues to provide clinical services to patients at the Atlanta VA Medical Center.

Dr. Richardson graduated from the University of North Carolina in 1989 and completed internship, residency, and fellowship training at the University of Florida. In addition, she received her master's degree in epidemiology from the University of Michigan in 1997.