Air travel in window seat raises DVT risk

7th February 2012 - One of the risk factors that can increase the risk of a deep vein thrombosis on a long-haul flight is sitting in a window seat, experts say.

The warning is part of comprehensive advice about the many risk factors for developing deep vein thrombosis (DVT), or blood clot, as the result of long-distance air travel.

Economy class syndrome

However, the American College of Chest Physicians says there is no conclusive evidence that the development of a DVT is more likely because of so-called 'economy class syndrome', or from enjoying an in-flight drink.

DVT is a serious condition that can lead to a potentially fatal blockage in the lung known as a pulmonary embolism. DVT usually occurs in a deep leg vein and causes pain and swelling in the leg. It can lead to a blood clot breaking off into the bloodstream and blocking one of the blood vessels in the lungs:  a pulmonary embolism.

Each year one in every 1,000 people in the UK is affected by DVT, but few of these are associated with flying.

The inactive passenger

Lack of physical movement is known to be a factor behind DVT, and the experts who reviewed existing clinical evidence found that the risk was highest among passengers who sat still during flights of more than eight hours.

They say it is not so much the type of ticket you hold but what you do once you are on the plane.

"Travelling in economy class does not increase your risk for developing a blood clot, even during long-distance travel; however, remaining immobile for long periods of time will," said Dr Mark Crowther of Master University, Ontario, Canada, who co-authored the guidelines.

He continued in a statement: "Long-distance travellers sitting in a window seat tend to have limited mobility, which increases their risk for DVT. This risk increases as other factors are present."

A panel drew up a list of these other risk factors, including:

• A previous history of DVT or pulmonary embolism
• Having cancer
• Recent surgery or trauma
• Old age
• Taking the contraceptive Pill, or other oestrogen use
• Being pregnant
• Obesity

The NHS says that being dehydrated also increases the risk of developing DVT. However, the panel found no conclusive evidence that this was the case. Neither did they find proof that having an on-board alcoholic drink, which can increase the risk of dehydration, raised the chances.

Guarding against DVT

Along with the risks, there are also recommendations for how to reduce the chances of DVT. The experts advise anyone at risk of DVT taking a flight of six hours or more should sit in an aisle seat, walk about as often as possible, stretch their calf muscles and wear below-the-knee compression stockings.

However, they advise against compression stockings for passengers not at risk of DVT.

The routine use of aspirin, which is sometimes recommended for reducing the chances of blood clots forming, or other anticoagulant therapy, is not advisable, the experts say. For those long-distance travellers who are at particularly high risk of DVT, anti-thrombotic medication should be considered on an individual basis, as the adverse effects may outweigh the benefits.

The guidelines are published in the February issue of the journal CHEST.