Air travel-associated venous thromboembolism.

Long-distance air travel is increasing and cases of venous thromboembolism (VTE) following air travel have attracted both considerable public attention and legal claims against airlines. VTE is a common disorder worldwide with a notably high incidence in older individuals. Many biochemical factors that lead to, or accentuate, thrombus formation are associated with increased risk of VTE. These factors include thrombophilia, activated protein C resistance and factor V Leiden, prothrombin gene mutation, antiphospholipid antibodies, protein S and protein C deficiencies, and methylene tetrahydrofolate reductase polymorphism and homocysteinemia. Individual physical characteristics including age, weight and height are significant for personal risk of VTE as are other factors such as use of oral contraceptives in women. In the case of air travel-related venous thrombosis, superimposed upon these individual factors are the environmental factors directly related to air travel. Travel-related factors include stasis associated with prolonged periods of immobility, physiological stresses resulting from exposure to the cabin environment (low humidity and hypoxia) in long-haul flight and other in-flight factors. It is suggested that passenger behavior (movement, avoidance of dehydration and of alcohol) and appropriate pharmacological prophylaxis for high-risk travelers can reduce the likelihood of VTE. Physical prophylaxis (use of compression stockings or in-flight exercise devices) may also be of general benefit to passengers. It is recommended that airlines become more proactive in educating passengers concerning the dangers of VTE and in promoting passenger actions that can reduce risk. Airlines should also work to avoid cramped seating conditions (seat size and pitch) that contribute to prolonged immobility. Governments and regulatory authorities should mandate the provision of adequate seating conditions and a good cabin environment and should support studies that will define risks and determine the efficacy of protocols to minimize dangers of VTE. Increased long-haul air traffic and an aging population suggest that travel-related VTE may present a growing healthcare threat and has highlighted a need for additional biomedical research into the causes and potential solutions to this problem.