Blood clots happen in the top seats too

By STUART DYE

Deep vein thrombosis can occur in business class and not just the cramped cheaper seating, the largest study into the condition shows.

The study of 878 volunteers in Britain and New Zealand found one in 100 passengers will suffer "clinically significant" deep vein thrombosis.

The result is nine times higher than the rate expected and is the clearest indication yet of the frequency of DVT in air travellers, which has been a source of anxiety among passengers for years.

But what struck researchers was how DVT occurred among people who had taken precautions against clotting, such as taking aspirin to thin the blood or wearing compression stockings to improve circulation in the legs.

Two of the nine volunteers who developed the condition had travelled in business class on a long-haul flight, giving the lie to the common belief that it occurs only among those in economy class.

"The term 'economy class syndrome' is now redundant, with a better term being 'air traveller thrombosis'," said author Professor Richard Beasley of the Medical Research Institute in Wellington.

Deep vein thrombosis describes a blood clot that forms in leg veins during long periods of sitting down. The clot then moves to the heart, lung or brain, causing a heart attack or stroke.

The researchers recruited volunteers aged between 18 and 70 who travelled at least 10 hours by plane over six weeks; the average was 39 hours of travel during this period.

The recruits were measured for a blood protein called D-dimer, which is linked to dangerous clotting, both before and after their flight.

Nine - or 1 per cent - developed deep vein thrombosis, five of which were leg clots. The other four had clots which had reached their lungs.

"It has finally confirmed beyond doubt the association between long- distance air travel and venous blood clots, also known as DVT and pulmonary embolism," said Professor Beasley.

The study, published today in The Lancet, also revealed that people who develop deep vein thrombosis on long-haul flights will do so without any warning or medical signs.

"Most people who develop a blood clot with travelling do not have recognised risk factors," said Professor Beasley.

"As a result it is not possible to predict who will be affected."

The New Zealand study took more than two years to complete.

Professor Beasley said the passengers were an "average group of adult travellers" with a low to medium risk of developing deep vein thrombosis.

"I would not have expected more than one event [blood clot] in this population."

Airlines insist there is no evidence of any specific link between flying and deep vein thrombosis. But many of them routinely advise travellers to drink water regularly, move their legs and wiggle their toes from time to time while seated, and get up occasionally to move around the cabin for exercise.

The condition was first spotted among survivors of the Blitz in World War II who slept in deck chairs in air-raid shelters. The problem stopped when the deckchairs, which pressed on the back of the legs, were removed.

Lead investigator Dr Rodney Hughes, based in Britain, said the study was unable to examine the effectiveness of different preventive measures that had been suggested.

"However, from the information available, it is now recommended that travellers undertaking long-distance flights should consider wearing compression stockings and do other simple measures such as regular foot exercises."

If travellers were concerned about their risk, they should consult their doctors before travelling.

Herald Features:
Economy class syndrome