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Study Bolsters Notion of 'Economy Class Syndrome'

More blood clots found in those who fly long distances

FRIDAY, Sept. 21, 2001 (HealthDayNews) -- Traveling in coach class can be more than merely uncomfortable: A new study says it can be dangerous.

People who fly longer distances are at far-greater risk of developing a blood clot in their lungs than those who fly shorter distances, the study found.

The researchers, whose findings were published in the Sept. 13 edition of the New England Journal of Medicine, painstakingly reviewed all passengers who landed at Charles de Gaulle Airport in Paris between November 1993 and December 2000.

They found that the incidence of pulmonary embolism -- the medical term for this potentially fatal blockage in a lung artery -- was 150 times higher among individuals who had traveled more than 3,100 miles (1.5 cases per million) than among people who had flown fewer than 3,100 miles (0.01 case per million). The incidence increased markedly, to 4.8 cases per million, among people who had traveled 6,200 miles.

All of the individuals who developed pulmonary embolism had traveled at least 2,480 miles, and three quarters had been wedged in economy class, where space is notoriously tight. Only three passengers (5 percent) reported that they had left their seats during the flight.

"There's been a debate in the literature as to whether air travel is really a risk factor, and this nails it," says Dr. Jack Ansell, a professor of medicine at Boston University School of Medicine. "Yes, it is a factor, and it correlates with distance traveled."

"I like the direct correlation between development of this syndrome and greater distance traveled. It's very scientifically done," adds Dr. Stanley Mohler, professor and director of aerospace medicine at Wright University School of Medicine in Dayton, Ohio. "We've been publishing on this for about six years, and the knee-jerk reflex reaction by various groups was that there wasn't anything to it."

The condition, which is now called "economy class syndrome," was first noticed among Londoners who spent long periods of time huddled in air-raid shelters during World War II. A link to air travel was reported in 1954. The link was solidified last October, when a 28-year-old British track star died of a pulmonary embolism in London's Heathrow Airport after a 12,000-mile flight from the Sydney Olympics.

Whether squashed in a bomb shelter or folded into an economy-class seat, the effects on our body are the same. Lack of movement -- or lack of movement combined with limited space -- causes blood flow in the legs to stagnate, occasionally leading to clots which can then break off and travel into the lungs (or elsewhere, though that wasn't the subject of the study).

Theoretically, this could happen in any number of settings, notes Dr. Jack Hirsh, director of the research center at Hamilton Health Sciences in Hamilton, Ontario. But there are additional risks associated with air travel, he adds, including the fact that pressurized cabins have low humidity, which contributes to dehydration.

Does the study argue for more leg room for budget travelers? "I don't know that this is going to change the configuration of seating," says Ansell. Most airlines are aware of the risk, some distribute literature about it, and others play in-flight exercise or stretch videos, Hirsh adds.

"We encourage people to get up and move around," says Dawn Deeks, spokeswoman for the Association of Flight Attendants. "But we're not equipped to handle 400 people doing calisthenics in the aisles."

Mostly, it's up to the passenger to take action. On long plane trips, Ansell advises you get up and walk around at least once an hour. Flex your muscles and stretch several times every hour. Also, drink lots of water and avoid alcohol and coffee, which can be dehydrating.

Pulmonary embolism can take days or weeks to manifest, and the researchers only looked at passengers who had developed the problem during the flight or within one hour after touching down and had used emergency medical services.

Nevertheless, Hirsh says, it's important to remember that the incidence of severe pulmonary embolism during air travel is extremely low. "For anything under five hours, the risk was extraordinarily low, so even traveling across the North American continent would be low risk," he adds. There are also predisposing factors. Seventy to 90 percent of those people who developed the condition had associated risk factors such as obesity or cancer.

"This is not an epidemic, but it is a serious problem and it's preventable," Ansell adds. "Those at highest risk are those with predisposing factors. But it can happen to anyone."

What To Do

For more information on staying healthy while traveling, visit the Aviation Health Institute.

For more information on pulmonary embolism, try the American Academy of Orthopedic Surgeons or Medline Plus.

SOURCES: Interviews with Stanley Mohler, M.D., professor and director of aerospace medicine, Wright State University School of Medicine, Dayton, Ohio; Jack Hirsh, M.D., director, research center, Hamilton Health Sciences, Hamilton, Ontario; Dawn Deeks, spokeswoman, Association of Flight Attendants, Washington, D.C.; Jack Ansell, M.D., professor of medicine, Boston University School of Medicine, Boston; Sept. 13, 2001, New England Journal of Medicine
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