Risk of Venous Thromboembolism After Air Travel

Abstract

Background: Conflicting data are available on air travel as a risk factor forvenousthromboembolism.Toourknowl- edge, there are no studies investigating whether individu- als with thrombophilia and those taking oral contracep- tives are more likely to develop venous thromboembolism during flights than those without these risk factors. Participants and Methods: The study sample con- sisted of 210 patients with venous thromboembolism and 210 healthy controls. DNA analysis for mutations in fac- tor V and prothrombin genes and plasma measurements of antithrombin, protein C, protein S, total homocysteine levels, and antiphsopholipid antibodies were performed. Results: In the month preceding thrombosis for pa- tients, or the visit for controls, air travel was reported by 31 patients (15%) and 16 controls (8%), with an oddsratio of 2.1 (95% confidence interval, 1.1-4.0). Thrombophilia was present in 102 patients (49%) and 26 controls (12%), and oral contraceptives were used by 48 patients and 19 controls (61% and 27% of those of reproductive age, respectively). After stratification for the presence of air travel and thrombophilia, the odds ratio for thrombosis in individuals with both risk factors was 16.1 (95% confidence interval, 3.6-70.9). Stratification for the presence of air travel and oral contraceptive use gave an odds ratio of 13.9 (95% confidence interval, 1.7- 117.5) in women with both risk factors. Conclusions: Air travel is a mild risk factor for venous thromboembolism, doubling the risk of the disease.When thrombophilia or oral contraceptive use is present, the risk increases to 16-fold and 14-fold, respectively, indi- cating a multiplicative interaction. Arch