According to the World Health Organization (WHO) the chances of developing deep vein thrombosis ( DVT) double after traveling for four hours or more; this says WHO equates to one in 6,000 long-haul passengers at risk of potentially dangerous blood clots.
Particularly vulnerable are tall people whose legs are jammed in economy class and very short people whose feet do not touch the ground, and it is the immobility during travel which creates the danger.
Also at greater risk are the obese, women on birth control pills, those with blood clotting disorders, frequent travellers and those who take very long journeys.
