Business travelers who fly frequently run risk of blood clots, study shows
By Tanya Mohn
Life-threatening blood clots and flying have been linked for more than 50 years, but a new study on business travelers who frequently fly confirms absolute risk for the first time, researchers have said.
People who fly four hours or more have three times the risk of developing clots, compared with periods in which they do not travel, said Frits Rosendaal and Suzanne Cannegieter, of Leiden University Medical Center, The Netherlands, the lead researchers in the study.
A blood clot that forms within large, deep veins of the body, usually in the leg, is called a deep vein thrombosis or DVT. If untreated, part of the clot may break off and travel to the lungs, where it can cause a pulmonary embolism, a potentially fatal condition.
"We now know out of 4,500 people who fly, one will get a DVT within 8 weeks after travel," Cannegieter said. "It's not really a huge amount," but the risk increases with the duration of a flight and the number of flights in a short period. The study tracked almost 9,000 employees of large international companies and organizations during a four- to five-year period. Results were published this fall in the online Journal PLoS Medicine; preliminary findings were reported in late June by the World Health Organization.
Obesity, extremes of height (shorter than 5'4" and taller than 6'4"), oral contraceptive use, hormone replacement therapy and inherited blood clotting disorders also increase risk. A combination of these factors "may increase risk 20- to 50-fold," Rosendaal said.