The risk of developing dangerous blood clots doubles after travel lasting four hours or more, research shows. The risk applies to plane, train, bus or automobile passengers who remain seated and immobile, the World Health Organization found. Blood clots can form in the lower limbs during long periods of immobility – and can kill if they travel to the lungs. But WHO cautions that the absolute risk remains relatively low – at about one in 6,000 passengers. Immobility Passengers taking multiple flights over a short period of time are also at higher risk, says WHO. This is because the risk of venous thromboembolism (VTE) – the collective name for DVTs and pulmonary embolisms (clots in the lungs) – does not go away completely after a flight is over, and risk remains elevated for about four weeks. The report, commissioned in 2001 shortly after media and public attention on VTE following the death from pulmonary embolism of a young English woman who returned on a long-haul flight from Australia, confirms that a number of other factors increase the risk of clots during travel. These include obesity, being very tall or very short (taller than […]