DAYTON, OHIO -- After sitting all scrunched up on that never-ending flight from Sydney or Rome, the pain in your leg might be only a fleeting muscle cramp.
But it also could be a symptom of "economy class syndrome," a serious but preventable hazard of frequent flying.
Awareness of the problem catapulted to the world stage when a 28-year-old woman died of it while claiming her baggage at London's Heathrow Airport. The amateur athlete was returning on a 15-hour flight from Sydney, Australia, where she had attended the Olympic Games.
According to Dr. Stanley Mohler at Wright State University School of Medicine, an international authority on aerospace medicine, the term "economy class syndrome" was coined to identify the effects of blood clots developed in the deep veins of the legs (deep vein thrombosis) after sitting for prolonged periods in cramped conditions -- notably the coach sections of commercial airplanes.
The condition isn't limited to air travel, however. It was described first in 1940 by British physicians who observed an increase in pulmonary embolism among people sitting in crowded air-raid shelters during the London "Blitz."
Until recently, economy class syndrome has been a "stealth problem," according to Dr. Mohler, director of Wright State's Aerospace Medicine Program. "It sneaks up on people. It can fool doctors during diagnosis because the presenting symptoms resemble other conditions."
The most common symptom is pain in the calf muscles developed during or shortly after a long airplane flight. The pain may be mistaken for a muscle cramp, but it can indicate formation of a deep vein clot resulting from sludging of blood in static leg muscles. Typically, the clot dissolves and pain subsides after air travelers reach their destination and have an opportunity to walk around.
"Most airplane passengers never know they experienced economy class syndrome," Dr. Mohler says.
In more serious cases, clot material reaching the lungs causes pulmonary embolism. Some experience flu-like symptoms (mild chest discomfort and coughing) which pass in a day or two as emboli dissolve. Others experience significant chest pain, which may be diagnosed and treated initially as a heart attack. In the worst cases, the blood clot blocks the pulmonary artery and may lead to heart complications and death.
No one knows how frequently deep vein clots occur among air travelers, according to Dr. Mohler. A 1986 study at London's Heathrow airport found that 18 percent of 61 sudden deaths among long-distance flyers resulted from blood clots. In 1994 Dr. Mohler and a colleague identified over 20 cases of economy class syndrome related directly to the physical restrictions of air travel.
One well-known case was that of former Vice President Dan Quayle, who developed pulmonary embolism in 1994 after a series of cross-country airplane flights.
Dr. Mohler believes that economy class syndrome is more common today as a result of two factors, the increase in the number of frequent flyers and airline deregulation. Seat pitch, the distance from one airline seat to the one in front of it, is no longer regulated by the Civil Aeronautics Board (CAB), which was abolished with deregulation. Airlines moved seats closer together to fit more passengers on planes. Seat pitch in the economy class now runs between 28-31 inches. The distance should be 40 inches, according to Dr. Mohler.
"As a result of crowded seating, tall people often sit with their knees touching the seat in front of them. Other passengers are reluctant to move around a crowded cabin during flights because it causes so much commotion," Dr. Mohler says.
Well-known risk factors for developing deep vein blood clots increase an air traveler's risk for economy class syndrome. These include a history of blood clots, cancer, prolonged bed rest following orthopedic surgery, recent treatment involving general anesthesia, estrogen therapy, obesity and cigarette smoking.
Dr. Mohler offers the following advice for preventing economy class syndrome on long flights:
- Book exit row, bulkhead, or aisle seats to get more leg room.
- Wear loose-fitting clothes and avoid knee-length stockings that constrict circulation.
- Avoid alcohol and caffeine, which contribute to dehydration during long flights. Drink plenty of other fluids.
- Walk up and down the aisle periodically.
- Massage feet, ankles, lower legs, and knees to move blood out of the legs and toward the heart.
- While seated, exercise calf muscles by clenching your toes.
According to Dr. Mohler, people at high risk of blood clots should consult their doctor about taking a half-strength aspirin to thin the blood before long flights.
"Some airlines are putting exercise guides in airplane seat backs," Dr. Mohler says. "Both the airline industry and the medical profession are beginning to make people more aware of this preventable hazard of air travel."
Editor's note: Wright State's Aerospace Medicine Residency Program is the world's longest running civilian program in this medical specialty. Supported by the National Aeronautics and Space Administration (NASA), it trains physicians for career paths with NASA, the Federal Aviation Administration (FAA), and the airline industry. In addition to resident-physicians from the U.S., the program has trained graduates from 18 foreign countries who hold leadership positions in aerospace and aviation medicine throughout the world.