Hot topic - DVT risk and air travel
19 December 2003 - written by Bupa's Health Information Team
A newly published study has revealed that up to 1% of all long-distance air travellers could develop symptoms of venous thromboembolism (deep vein thrombosis [DVT] or pulmonary embolism). The New Zealand research was published in the 20/27 December 2003 issue of The Lancet. The researchers also found that travellers in business class, as well as those in economy class, were affected. This suggests that the term "economy class syndrome" may have to be changed to "air travellers' thrombosis".
What is "economy class syndrome"?
When a vein is damaged or blood flow in a vein slows or stops, a blood clot may form. Normally a clot will form in a vein contained deep in the leg. Because of this the formation of such a blood clot is known as deep vein thrombosis (DVT). When DVT develops in a passenger who has flown long distance it is often referred to as "economy class syndrome".
Occasionally a blood clot may break away from a vein in the leg and travel up the vein. When this happens it may end up blocking a blood vessel in the lung, resulting in a condition known as pulmonary embolism.
With the right treatment it is rare for DVT to lead to pulmonary embolism (PE).
Both DVT and PE are described as symptomatic venous embolism.
For more on DVT and PE, please see Bupa's DVT factsheet:
http://hcd2.bupa.co.uk/fact_sheets/html/deep_vein_thrombosis.html
What are the effects of deep vein thrombosis and pulmonary embolism?
Deep vein thrombosis
A blood clot in the leg may either partially or totally block the vein, leading to:
- swelling of the leg
- warmth and redness of the leg
- pain that is noticeable, or worse when standing or walking
- sometimes, it can cause no symptoms at all.
Pulmonary embolism
Depending on the size of the blood clot, it can range from a minor to a life-threatening condition. A clot in a blood vessel in the lung may cause:
- shortness of breath
- chest pain which may be worsened by deep breaths
- coughing up phlegm, possibly flecked with blood
Why are these problems associated with long-distance air travel?
On long-distance flights, people are required to sit in the same seat for long periods of time (often more than four hours at a time). This can cause the blood flow in the veins in the leg to slow down, and may promote the formation of blood clots. It has been noticed that long-distance air passengers are at greater risk of developing DVT than people who do not fly long distances.
What is the risk of developing a blood clot associated with air travel?
Research published in July 2003 suggested that up to 10% of all long distance air travellers had shown signs of raised levels of clot-forming proteins in their blood. These people did not show physical signs having blood clots, but the raised levels indicate that they may be at a raised risk of forming clots.
For more on this research, please read our news story: "DVT plane risk may be lower than thought".
http://www.bupa.co.uk/health_information/html/health_news/110703dvt.html
This latest research - published in the 20/27 December issue of The Lancet - suggests that the risk of actually developing the physical signs of a blood clot (DVT or pulmonary embolism) is roughly 1%. The New Zealand researchers studied 878 people who travelled for at least four hours at a time. Over a six-week period the travellers flew for an average of 39 hours and all of them clocked up at least 10 hours in total. Nine of the travellers (1% of the total) showed signs of venous thromboembolism after flying. Of these, four had pulmonary embolism and five had DVT. Six of the passengers with venous thromboembolism had pre-existing clinical factors for developing the condition.
Is this problem only associated with air travel?
No. Because blood clots can form when the blood flow is slowed or stopped, any form of travel that requires people to stay in the same position for a long period of time may raise the risk. For example, it is believed that travelling long distances in coaches, trains and lorries may increase the risk as well.
Why has it been known as "economy class syndrome"?
Economy-class passengers have less legroom, and therefore less chance to keep the blood in their legs flowing by stretching and moving their legs. Because of this it was thought that they were more likely to develop DVT than their business-class fellow travellers. For this reason, the term "economy class syndrome" was coined.
Is "economy class syndrome" correct?
No. It now appears that the condition can affect business-class passengers as well. The latest research showed that two of the nine people who developed either DVT or pulmonary embolism had flown exclusively in business class.
The New Zealand study researchers argue that: "The term 'economy class syndrome' is now redundant, with a better term being 'air-traveller's thrombosis'."
What can be done to minimise the chances of developing a blood clot when flying?
Current advice includes:
- avoiding sitting still for long periods - during the flight it may help to move around the aircraft from time to time and do some inflight exercises
- keeping hydrated by drinking sufficient water or soft drinks
- considering wearing graduated compression stockings for longhaul flights. These need to be fitted to the size of the calves, not the foot size - and they aren't suitable for people with arterial disease. Also the research evidence for their effectiveness is not overwhelmingly convincing at the moment - see below
- considering taking aspirin before and after a longhaul flight, but more research is needed to confirm how effective this is - see below
- seeking your GP's advice before flying if you have any medical condition that is a known risk factor for DVT.
However, the latest research from New Zealand casts some doubt on how effective these measures are:
- five of the nine travellers who developed venous thromboembolism had used aspirin
- four of the nine travellers had worn compression stockings.
For more information on DVT, pulmonary embolism and air travel, please use the links below.
Links for more information
- Bupa DVT factsheet
- Bupa DVT article
- The Lancet website
- Department of Health DVT information
- Qantas in-flight exercise guide
