MONDAY, Sept. 24, 2007 (HealthDay News) -- Despite recent media reports of airplane passengers developing serious blood clots in-flight, only about one in 5,000 people are at risk for these types of events, a new study finds.
This type of leg clot, called a venous thrombosis, has gotten a lot of recent attention. In fact, the condition has been nicknamed "economy class syndrome," since it's been linked to long hours of immobility during flight.
But the actual risk for the condition hasn't been known.
In this new study, European researchers calculated the risk and found that for most people, the risk for so-called "economy class syndrome" was actually very small. However, the odds of in-flight clot are higher for some groups than others, and knowing your risk is important to accurately assessing whether you should take preventive measures, the researchers said.
"People who make several flights in a short time frame, people who make very long flights, women who use oral contraceptives, people who are overweight and people who are either short or very tall are at increased risk," noted lead researcher Dr. Frits R. Rosendaal, from the department of clinical epidemiology and hematology at Leiden University Medical Center, The Netherlands.
Venous thromboembolism is a condition where blood clots form in the veins of the legs. The danger is that these clots can break loose and travel to the lungs, heart or brain causing a life threatening condition. These clots can develop from prolonged sitting.
In the study, Rosendaal's team collected data on almost 8,800 people who worked for international companies and traveled a lot. These individuals were followed for a total of 38,910 person-years, during which they went on more than 100,000 long-haul (more than 4 hours duration) flights.
During follow-up, 53 thromboses occurred -- 22 within eight weeks of a long-haul flight. Rosendaal's group used this data to calculate the risk of having a thrombotic event. That risk: one event per every 4,656 long-haul flights.
The researchers found that the risk increased with more flights taken during a shorter period of time. It also increased with the length of flights. The risk was particularly high for those under age 30, women who used oral contraceptives, and individuals who were particularly short, tall, or overweight, Rosendaal said.
In addition, the risk of thromboses was highest in the first two weeks after the travel and after eight weeks post-travel, according to the report in the September issue of the online journal, PLoS Medicine.
Rosendaal noted that although the risk to individuals is very small, some people are taking precautions that he called "over the top."
"People should lighten up," he said, referring specifically to people who take aspirin before flying.
There is no evidence that blood-thinning aspirin prevents venous thrombosis, but it can cause abdominal bleeding, Rosendaal cautioned. "People shouldn't take aspirin for this -- it doesn't work," he said.
There is really no known preventive measure for economy class syndrome, Rosendaal said. The best advice is to move your legs and feet. There is no proof that elastic stockings and leg bands work, either, he noted.
Taking the blood thinner heparin will prevent venous thrombosis, too. But it can trigger bleeding and that risk outweighs its small benefit in preventing an in-flight venous thrombosis, Rosendaal said.
"The only thing that makes sense is to move your feet," he said.
One expert believes the risk of venous thrombosis from air travel is tiny compared with more common causes.
"This large, rigorously-conducted study was carried out by one of the world's top clinical research groups in venous thromboembolism," said Dr. Samuel Z. Goldhaber, a professor of medicine at Harvard Medical School and director of the Venous Thromboembolism Research Group at Brigham and Women's Hospital in Boston.
The risk of about one in 5,000 long-haul flights "is a tiny risk compared with the risk of venous thromboembolism from obesity, severe medical illness, cancer, or surgery," he said.
"More emphasis is required to prevent venous thromboembolism that occurs under everyday circumstances," Goldhaber said. "A heart-healthy lifestyle, emphasizing ideal body weight, sound nutrition, and daily exercise is a good way to start," he said.
More information
To learn more about venous thrombosis, visit NASA Occupational Health.
