Long-distance air travel doubles risk of blood clot

GENEVA: Flights lasting more than four hours about double a traveller’s risk of life-threatening blood clots, World Health Organisation studies found.

The clots, called venous thromboembolism, can form in the legs and can be fatal when they move into a patient’s lungs. The risk of VTE also applies to travel such as car, bus and train where passengers are seated for long periods, the Geneva-based agency said in an e-mailed statement.

More than 6,00,000 people in the US have a pulmonary embolism every year and more than 60,000 of them die, according to the country’s National Institutes of Health. The disorder is one of the most common causes of death in bed-bound hospitalised people. Long airplane journeys or car trips, childbirth within the last six months as well as use of drugs including oestrogen and birth control pills have also been linked to clots.

“There is a clear need for travellers to be given appropriate information regarding the risks and for further studies to identify effective preventative measures,” the Geneva-based agency said.

The conclusions announced on Friday were the result of the ‘WHO Research Into Global Hazards of Travel’, or WRIGHT, project aimed at confirming previous studies linking VTE and air travel. The project also sought to determine the extent of the risk.

The latest studies found the absolute risk of a healthy individual developing such a clot on a flight lasting more than four hours was one in 6,000. The studies looked at various groups of people, including Dutch commercial pilots, employees of international organisations and carriers of frequent flyer cards.

The global health body called for travellers to be given appropriate information regarding the risks, and a second phase of the project will focus on ways of reducing the chances of developing clots.

The current standard advice given to passengers encourages leg exercise.The WHO said the studies involved more people than previous research into the link between VTE and travel and enabled investigators to quantify the risk. Some people may be more prone to developing clots during long airplane trips, the WHO said.

The research found that pre-existing factors such as obesity, the use of oral contraceptives and blood abnormalities significantly increased the risk of developing DVT as a result of travel. The duration of travel and taking several flights within a short space of time also increased the likelihood of a clot forming.

A connection between air travel and VTE was first detected in 1954. The condition can cause medical problems ranging from pulmonary embolism, or clots in the lungs, and deep vein thrombosis to stroke.

VTE is often dubbed “economy class syndrome” after health officials recognised a link to airplane passengers on long flights, particularly in the back of the plane where leg room and seating are cramped, according to the American Heart Association. Passengers in business and first class also may be susceptible to clots.