One Thrombosis Develops for Every 4,500 Long Flights

Study reports absolute risk of thromboembolism after air travel

WEDNESDAY, Sept. 26 (HealthDay News) -- Flights lasting more than four hours moderately increase the likelihood of venous thromboembolism, with a risk of roughly one event for every 4,500 flights, according to a report published in the September issue of PLOS Medicine.

Saskia Kuipers, M.D., of Leiden University Medical Center in the Netherlands, and colleagues followed 8,755 employees of international companies for an average of 4.4 years, relating the incidence of symptomatic venous thromboses with exposure to long-haul flights, defined as flight time of at least four hours.

During the follow-up period, 53 thromboses occurred. The incidence rate of venous thrombosis within eight weeks of a long-haul flight was 3.2 per 1,000 person-years compared to 1.0 per 1,000 person-years in individuals not exposed to air travel. This correlated with a risk of one venous thrombosis per 4,656 long-haul flights. Risk was increased with longer flights and more flights within a short time frame.

"The results of our study do not justify the use of potentially dangerous prophylaxis such as anticoagulant therapy for all long-haul travelers, since this may do more harm than good. However, for some subgroups of people with a highly increased risk, the risk-benefit ratio may favor the use of prophylactic measures," the authors conclude.

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