Page last updated: 2008-8-31
AircrewHealth.comDeep Vein Thrombosis (DVT) is a blood clot that forms in a large vein, usually deep in the body. The most common location is a vein in the leg or hip, although they can occur elsewhere in the body.
Such a clot can impede circulation in the area around the clot. This can make the area around the clot painful and swollen.
But the most serious problem results when the clot (or a piece of it) breaks free, and travels through the bloodstream. When this happens, it can lodge in the lung, causing a blockage. This is a serious and potentially fatal condition called pulmonary embolism.
In general, DVT results from sluggish blood flow and/or a tendency for the blood to clot.
A number of health conditions can be associated with poorer circulation and/or clotting, e.g., cardiovascular diseases, certain cancers, rheumatoid arthritis, certain kinds of injuries, current or recent infections, inflammation. In addition, pregnant women, smokers, women taking oral contraceptives, and people who are obese can be more susceptible to poor circulation and clotting.
Unfortunately not all people who have one or more of those risk factors know that they have them. Those who do know that they have these conditions often do not understand that they may be at risk for DVT as a result.
And by the way, people who already have had a DVT are considered to be at risk for another episode.
The majority of documented cases of DVT associated with flying have happened in passengers -- not crew -- who had other risk factors such as pre-existing cardiovascular disease, clotting disorders, current or recent infection, dehydration, and so on.
Documented cases of DVT in airline passengers are associated with long flights during which the passenger stayed relatively immobile or in one position for a long time.
Blood circulation in the legs slows down during lengthy periods of immobility.
For passengers, the key factors seem to be long periods of inactivity and immobility, coupled with dehydration.
First of all, both Pilots and Flight Attendants tend to be very healthy and free of relevant risk factors, almost by definition (else they would be unable to continue to work in their flying jobs).
Flight Attendants rarely -- if ever -- sit in one position for long periods of time while in the air. Pilots do tend to sit for longer periods than Flight Attendants, however they are generally more active than passengers, even while seated.
On long flights, it is important to move about from time to time, where possible, in order to stimulate circulation -- especially in the legs. Many carriers now include in their in-flight magazines a page illustrating simple exercises that passengers can do while seated, in order to improve their circulation on long flights.
Dehydration can add to the risk of clotting, so it is important to drink plenty of fluids -- especially water -- before and during a long flight. Consumption of beverages containing alcohol or caffeine should be minimized, if not avoided outright.
Some travel medicine doctors recommend that people who are at risk take an aspirin before and during a long flight as a preventive measure against DVT. Aspirin is known to have "blood thinning" properties. It acts to prevent blood cells from sticking together, which is why it also is recommended for people at risk for heart attacks.
However, there is no official agreement in the medical community on whether or not this is a good idea for DVT prevention. In fact some believe it may cause more harm than good, since aspirin also can irritate the lining of the stomach and cause internal bleeding.
Wearing compression stockings during long-haul flights may be of some benefit, especially for passengers who have one or more risk factors for DVT.
Click here for recent news stories and media releases about Deep Vein Thrombosis (DVT).
Here are some reliable and credible on-line sources of information about Deep Vein Thrombosis .
Deep Vein Thrombosis and Travel - FAA Civil Aerospace Medical Institute 
[PDF format]
Venous Thromboembolic Disease: Risk for Passengers and Aircrew? - FAA, August, 2005
Deep Vein Thrombosis - AFA-CWA: Air Safety, Health & Security Dept., March, 2004
Dept. of Health Report - Review on Aspirin and Deep Vein Thrombosis - UK Dept. for Transport, 2004
Holiday Travel: Avoiding Deep Vein Thrombosis DVT - MedicineNet.com, 2004
Public perceptions of Deep Vein Thrombosis (DVT) - UK Dept. for Transport, 2004
Pulmonary Embolism and Deep Vein Thrombosis - article for patients
by S. Goldhaber & R. Morrison, Circulation, 2002; 106: 1436-1438. ©
American Heart Association, Inc. [PDF format]
Flight-related Deep Vein Thrombosis (DVT)- Economy Class Syndrome - NASA Occupational Health, 2001
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