September 25, 2007 - The risk of developing venous thromboembolism while flying on an airplane, a condition known as “economy class syndrome,” is only about one in 5,000 for long flights, although the odds of in-flight clot are higher for some groups, according to a new study out of The Netherlands.
“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 Frits R. Rosendaal, M.D., Ph.D., from the department of clinical epidemiology and hematology at Leiden University Medical Center, The Netherlands.
In the study, Rosendaal's team collected data on almost 8,800 people who worked for international companies and traveled often. 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.
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," said Samuel Z. Goldhaber, M.D., a professor of medicine at Harvard Medical School and director of the Venous Thromboembolism Research Group at Brigham and Women's Hospital in Boston.
Source: Frits R. Rosendaal, M.D., Ph.D., Leiden University Medical Center, Clinical Epidemiology and Hematology, The Netherlands; Samuel Z. Goldhaber, M.D., professor of medicine, Harvard Medical School, director, Venous Thromboembolism Research Group, Brigham and Women's Hospital, Boston; Sept. 24, 2007, PLoS Medicine
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November 21, 2022 
