- The Washington Times - Wednesday, March 14, 2001

GENEVA Medical experts and representatives from major international airlines said yesterday there's likely a link between long airline flights and deadly blood clots, and that a study to examine the connection will commence immediately.

At a session organized by the World Health Organization, the experts and representatives from 16 major airlines agreed that air travel and deep vein thrombosis probably were linked and decided to begin a long, three-part study.

"Realistically, I think we're looking at 18 months to two years to complete an epidemiological study of that size," said John Scurr, consultant surgeon at Middlesex and University College Hospital in London. "The amount of research actually done is limited, and this will be a huge project.

"The study will need to look at passengers before they get on an airplane and after they get off to see who actually develops blood clots."

Deep vein thrombosis is a condition in which a blood clot forms in the deep veins of the legs. It becomes deadly when part of the clot breaks off and blocks a blood vessel in the lungs, known as thromboembolism.

Observers say passengers on long flights, of eight hours or more, may be at particular risk because they sit still for long periods.

The syndrome is the second-leading cause of the small number of deaths on airplanes, after heart attacks, said Dr. Glen Roseborough, assistant professor of vascular surgery at Johns Hopkins University Medical Center in Baltimore.

In Britain alone, the British Travel Health Association estimates that about 2,000 airline passengers die annually from the blood clots. A surgeon from Sydney's St. Vincent Hospital in Australia estimated 400 passengers arriving at Sydney's airport develop the disorder each year.

Some airlines have begun showing videos about the condition to instruct passengers on ways to decrease their risk.

Inaccurately termed "economy-class syndrome" because it was believed the cramped conditions in coach class caused the blood clots, deep vein thrombosis can occur among business- and first-class passengers, as well as those who sit for extended periods in buses, cars and at desks.

"There is no evidence that blood clots are specifically related to the position in the plane, the seat pitch, the seat size," Dr. Scurr said.

A first study will look at the incidence of blood clots in passengers, while another will try to determine whether being in an airplane provides specific risk factors, such as changes in cabin pressure and low-oxygen levels.

The third study will assess the effects of preventive measures, such as exercise, wearing circulation-stimulating stockings or taking blood-thinning agents.

"Tens of thousands, possibly as many as hundreds of thousands of passengers, will need to be studied to get definitive answers," Dr. Scurr said.

Medical experts are not sure how long humans must stay still to be at risk, although risk factors include age, obesity, smoking, pregnancy, cancer, recent surgery, hormone therapy or a history of the disease.

About one of every six persons who develops the syndrome eventually dies unless treated, Dr. Roseborough said. Often the victim mistakes leg soreness caused by the condition for cramps and does not seek medical treatment, sometimes with fatal results.

The most effective preventive measure is exercising the feet and legs at a seat to improve circulation, authorities agreed. They also recommended drinking lots of water and avoiding alcohol. They disagreed over whether taking aspirin helps.

Recent deaths linked to deep vein thrombosis have sparked class-action lawsuits against major international airlines. An Australian law firm has prepared compensation claims against six airlines for about 1,000 persons who claim to have suffered deep vein thrombosis while on flights.

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