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Ashford Hospital, near London�s Heathrow airport, has reported around thirty deaths in the last three years. That amounts to nearly one death per month among passengers of between 28 and 80 years of age arriving on flights lasting more than six hours.

In Tokyo international airport�s hospital, there have been as many as 25 deaths reported in the last eight years. But in Spain, AENA assures us that, to date, no case has been reported.

On the whole, passengers who are either old, overweight, with varicose or damaged veins in their legs or who are prone to swollen legs, heavy drinkers or women taking birth control pills are most at risk of this syndrome.

In fact, what we are talking about is deep vein thrombosis (DVT) or, to put it another way, a clot in the blood vessels of the lower limbs (deep veins). And what causes it? Cramped seating, lack of legroom and the enforced immobility experienced on most long haul flights, although that does not mean to say that this couldn�t happen in any other form of transport

In fact British Airways, who has decided to include a warning on their tickets reminding passengers of the need to do some exercise during long flights, points out that circulation problems caused by maintaining the same position for too long could also occur on a train journey or in a car.

What are the symptoms and when do they occur?
It begins with pains in the calves, cramp or reddening of the skin, and can turn into a pulmonary embolism, irreversible damage or even death if the clot reaches the heart, lungs or the brain.

While symptoms can appear immediately, there have been cases where they have taken days or even weeks to show up.

Preventative measures
According to experts in cardiovascular diseases the best way to avoid a thrombosis such as this, is by moving around. The Aerospace Medical Association�s Medical guidelines for airline travel, published last year in Spanish by Iberia�s Medical Service advises travellers of the following: �Do not place luggage under the seat in front. Exercise your legs at regular intervals. Do not sleep in a cramped position. Do not take sedatives and drink plenty of liquid but avoid alcoholic drinks�.
Ideally you should walk up and down the aisle at least once an hour.
It is also advisable to stretch your arms and legs while in your seat and to stand up every now and then.
Here is a simple exercise you can do: with your heel firmly on the floor quickly raise your foot and wiggle your toes. Then do the opposite: raise your heel keeping your toes on the floor.
Unless you are allergic or suffer from�stomach ulcers, taking an aspirin before takeoff can help to prevent clots thanks to its blood thinning properties.
On night flights it is not�a good idea to take sleeping pills. There is less oxygen on board a plane than on the ground and your heart rate may slow down if you take barbiturates.
The consumption of alcohol adds to dehydration already caused by there being less oxygen in the air. Water and soft drinks are always a better choice than spirits or any drinks containing alcohol.