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DVT risk doubles after four hours on a plane

WHO research shows DVT risk increases with travel by plane, train, bus or car

OnMedica Staff

Friday, 29 June 2007

The risk of developing life-threatening blood clots doubles after four hours seated on a plane, research from the World Health Organisation (WHO) shows.

The research found that passengers of planes, trains, buses and cars are all at higher risk of venous thromboemebolism, such as deep vein thrombosis or pulmonary embolism, when they remain seated and immobile on journeys of more than four hours. This is because prolonged immobility causes a stagnation of blood in the veins which can promote blood clot formation.

However, the WHO Research into Global Hazards of Travel (WRIGHT) project, commissioned in 2001 in response to rising public concern about risk of venous thromboemebolism on cramped long-haul flights, so-called 'economy class syndrome', found that the absolute risk if seated and immobile for more than four hours was still relatively low at about 1 in 6000.

The project also found that people who took multiple flights over a short period of time were at higher risk because the elevated risk of venous thromboemebolism did not go away completely after a flight for about four weeks.

Other factors found to increase the risk of venous thromboemebolism during travel included obesity, being very tall or very short (taller than 1.9 meters or shorter than 1.6 meters), use of oral contraceptives, and inherited blood disorders leading to increased clotting tendency.

Dr Catherine Le Galès-Camus, WHO Assistant Director-General for Non-communicable Disease and Mental Health, said: "The study does confirm that there is an increased risk of venous thromboembolism during travel where the passenger is seated and immobile for over four hours, whether in a plane, train, bus or car. However, it is important to remember that the risk of developing VTE when travelling remains relatively low.

The project did not investigate the effectiveness of preventive measures against venous thromboemebolism, such as the use of compression stockings or doing leg exercises.

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