Summary

Whether long-distance travel and symptomatic venous thromboembolism(VTE) are associated is debated. On the basis ofthe available literature a fair risk estimate cannot be obtained.We estimated an accurate odds ratio for the relationshipbetween recent travelling and symptomatic VTE.From three case-control studies consisting of 788 and 170patients with clinically suspected deep vein thrombosis (DVT)and 989 patients with clinically suspected pulmonary embolism(PE) referred for diagnostic work-up, a pooled odds ratio forthe relation between travel and symptomatic VTE was calculated.Cases were patients in whom the diagnosis was confirmedaccording to a diagnostic management strategy, whereas controlswere patients in whom the diagnosis was excluded andwho had an uneventful clinical follow-up. Patients were seen in the period April 1997 to September 2000. Travel history wasrecorded prior to diagnostic work-up.The pooled odds ratio for the association between any traveland symptomatic venous thromboembolism was 0.9 (95% CI:0.6-1.4).The median travel time was 7 h (quartile range 4 to 10h). Separate analyses performed for different types of transport(plane, car, bus or train) yielded comparable odds ratios. Theanalysis for duration of travelling showed an increased oddsratio of 2.5 (95% CI: 1.0-6.2) in the category of 10-15 h of travelling.This study shows that the average traveller does not have anincreased risk for symptomatic venous thromboembolism. Onlyvery long travelling (more than 10 h) may be associated withvenous thromboembolic disease.