Airline flight and Deep vein thrombosis (DVT)

A lot of people worry about getting DVT when travelling on a plane and that is not surprising because there has been a lot written in the press about it in the last few years and some of the stories have been quite alarming. Fortunately there have been some well- run scientific studies completed which give us more information about the actual risks for DVT after airline flight, and the risks and benefits of some of the things we can do to prevent them.

DVT after airline flight as been referred to as ‘economy class syndrome’ and it is thought to be caused by long periods of immobility in cramped conditions. Other factors thought to play a part include dehydration and lower air pressure in aircraft at high altitude.

The risk of a DVT forming is not just related to the period of the flight itself, but persists for several weeks after travel.

In any event the main message is that although we think air travel does increase the risk of DVT, the actual risk of getting a DVT after a flight is still very low. Some studies have shown that minor clots do occur in the small calf veins of passengers as frequently as one in 20 people, but the risk of these tiny clots going on to produce significant DVT’s is very low indeed. It is difficult to get a precise estimate but a recent Dutch study estimated the risk to be approximately one DVT for every 4,500 flights longer than 4 hours duration.

This is important because the key issue is what measures a person should take to prevent a DVT after flight. For example simple measures like wearing a pair of flight stockings or getting up every so often to walk around the cabin or drink some water is quite sensible and don’t carry any risk. However the use of tablets like aspirin, warfarin or injectable anti-coagulant drugs does carry a risk of bleeding, so before resorting to such measures one has to be confident that the risk of getting a DVT is worse than the health risk from the medication.

Some patients are at higher risk than others. For example patients who have previously had a DVT, patients with co-existing medical conditions that make a DVT more likely (such as a known cancer) or patients who are overweight or smokers are all at higher risk of DVT. Patients taking some types of drugs (most commonly the oral contraceptive pill or HRT) also have slightly higher risks of contracting a DVT in general and it is probably correct to assume that their risk after long haul flight is also greater than people who do not have any of these conditions. The exact precautions higher risk patients should take when embarking on long haul flight need to be assessed on a case-by-case basis depending on the individual risk factors involved.

In addition patients who have had a recent operation on the leg are probably at greater risk than the background population, and, it is for this reason that, in our practice, we recommend that patients do not fly long haul within 4 weeks of varicose veins surgery.


This post was written by Eddie Chaloner.  Eddie is a consultant vascular surgeon at Radiance Health, a vein treatment centre specialisng in the latest minimally invasive procedures for treating varicose veins, thread veins, and DVT.