Venous thromboembolism and travel: is there an association?

This paper reviews the literature on the association between venous thromboembolism and travel. There are plausible physiological reasons why sitting still for long periods (particularly in the cramped conditions of most aircraft) might predispose to venous thromboembolism. This may have been the explanation for the apparent excess of deaths from pulmonary embolism seen during the first months of the London blitz. No published controlled studies of thromboembolism and travel were identified, but eight case reports were analysed. They covered 25 people aged from 19 to 84 years with deep vein thrombosis or pulmonary embolism following travel. The reports suggest that long journeys are a particular risk and that there are often no symptoms until many hours after leaving the plane (so conventional methods of assessing the hazards of air travel may underestimate the problem). It is concluded that the literature tends to support the hypothesis that venous thromboembolism is associated with travel, but that carefully controlled studies are needed to test this properly.