Travel as a risk factor for venous thromboembolic disease: a case-control study.

Background: The link between travel and the risk of venous thromboembolic disease (VTED) has been widely suspected. However, only cases or series of cases have been reported in the literature.
Study Objectives: By means of a case-control study, we sought to confirm this relationship and to determine the main features, if any, of these posttravel VTEDs.
Design: The history, in particular the history of recent travel, of 160 patients presenting in our department with VTED was scrupulously investigated. All journeys undertaken during the preceding 4 weeks and lasting > 4 h by whatever means of transport were considered. The same questionnaire was submitted to a control group.
Results: When the two groups of patients are compared, a history of recent travel is found almost four times more frequently in the VTED group (p < 0.0001). The odds ratio for having a VTED in patients who traveled was 3.98 (95% confidence interval, 1.9 to 8.4). Means of travel used included the train in 2 cases, airplane in 9, and car in 28. Mean duration of travel was 5.4+/-2.1 h. These posttravel VTEDs are not confined to a specific location, seem to involve no particular predisposition, and are more often "idiopathic." This fact supports the hypothesis that travel alone can produce vein clot formation.
Conclusions: A history of recent travel is a risk factor for VTED. Posttravel venous thrombotic events can occur after short journeys in patients with no other risk factors or concomitant disease