The World Health Organization (WHO) released results from a research project warning that the risk of developing fatal blood clots during travel doubles after the passenger has been seated for four hours or more.
The condition, known as venous thromboembolism (VTE), involves first the formation of a clot, or thrombosis that develops in a deep vein ? usually the leg, according to WHO. This condition, called Deep Vein Thrombosis (DVT) can be potentially life-threatening if the thrombosis then breaks off and travels through the body to the lung where it becomes lodged and blocks blood flow. This latter condition of VTE is known as pulmonary embolism. Symptoms of DVT are pain, tenderness and swelling, while symptoms of the embolism include chest pain and difficulty breathing.
?The study does confirm that there is an increased risk of venous thromboembolism during travel where the passenger is seated and immobile over four hours, whether in a plane, train, bus or car,? said Dr. Catherine Le Gal?s-Camus, WHO Assistant Director-General for Noncommunicable Disease and Mental Health.
At the same time, she noted that ?it is important to remember that the risk of developing VTE when traveling remains relatively low.? Even with the increased risk, the absolute risk of developing VTE, if seated and immobile for more than four hours remains at about 1 in 6000.
The findings come from Phase I of the World Health Organization Research into Global Hazards of Travel Project. The first phase aims to confirm whether the risk of VTE is increased by air travel and to determine the magnitude of the risk.
In addition to travel lasting more than four hours, other factors contributing to the possibility of developing VTE include obesity, use of oral contraceptives and a family history of increased clotting tendency, WHO said. As the risk of VTE remains elevated for about four weeks after a trip is over, those who travel multiple trips of short periods of time are also potentially at risk.
The study did not explicitly investigate preventative measures against DVT and VTE, but the experts said that up-and-down movements of the feet at the ankle while seated can promote blood circulation. Upon receiving additional funding, further studies needed to identify effective preventive measures will begin under Phase II.
The report calls for transport authorities, airlines and medical professionals to inform travelers of the conditions and risk of VTE.