Sitting for long periods, particularly for over five hours in an aircraft, bus, train or car can lead to a condition called deep vein thrombosis or DVT. The combination of cramped seating, immobility, dehydration and reduced oxygen pressure at high altitude can cause blood clots to form, typically in the veins of the legs. If a piece of a clot breaks off and travels to the lungs the consequences can be severe, even fatal.
Travellers who have previously had a DVT may be advised to take anti-coagulant medication before the flight to reduce their risk.
DVT Prevention Tips