John Scurr, the consultant surgeon who carried out the study, said he was 'startled and concerned' by his findings. His report, the first project of its kind, will shock the travel industry and the millions who fly from the UK each year, many packed tightly into cheap seats.
Its results have been presented to a House of Lords inquiry which is expected next week to make the first official link between economy-class flying and deep vein thrombosis-DVT.
The Science and Technology Committee report will make wide-ranging recommendations and suggest that even first-class passengers are at risk.
Airlines, many of which have denied there is a danger, are likely to be urged to tell passengers of simple precautions they can take to prevent the condition.
Last night the Government said the Departments of Health and Transport are to launch a major joint inquiry in response to growing worries.
A spokesman Said: 'Clearly any Suggestion that flying over long periods can cause medical problems is a matter for concern.' Deep vein thrombosis is a blood clot in a major vein, usually in the legs or pelvis.
If the clot moves through the bloodstream it can cause a fatal pulmonary embolism - an obstruction of a blood vessel in the lungs.
Around half of all DVT victims have early Symptoms like swelling. But others show no sign of a clot until a major problem develops.
Mr Scurr, 50, consultant surgeon at Middlesex Hospital, said: 'It is like a ticking timebomb. Some find themselves in hospital years later with an ulcer in their legs, others die suddenly from a pulmonary embolism.
'By then it is so long since the flight that the link is often not made, so we do not know really how many passengers it has killed.
'We were able to give our passengers drugs and other treatments to dissolve the clots, but there may be thousands of people out there who do not realise they've got DVT.'
The issue was shockingly highlighted last month when bride-to-be Emma Christoffersen, 28, died from a blood clot minutes after a stepping off a 23-hour flight from Sydney.
The Daily Mail has uncovered two more recent DVT deaths of previously healthy passengers an the gruelling Australia flights.
Maureen Golding, 66, collapsed in June this year during a refuelling stop in Hong Kong. Jennie Metcalfe, 56, died at Heathrow in March 1998.
Major hospitals close to Heathrow receive at least two long-haul passengers a week with blood clots.
East Surrey Health Authority, whose hospitals cover the Gatwick catchment area, recorded 142 DVT deaths between April 1999 and April this year. It is believed a high number had been on long-haut flights.
The passengers in Mr Scurr's research were all over 50, but none had heart disease or other illnesses which put them at higher risk.
The surgeon said: 'I believe that the risk is one in ten for all passengers, not just those over 50.
Mr Scurr, whose findings will be published in The Lancet next month, is calling for a wider survey of all age groups.
His concern was echoed by George Geroulakos, consultant vascular surgeon at Ealing Hospital in West London. He has established that, of 75 patients admitted with DVT in the last eight months, some ten per cent had just taken long-haul flights.
Mr Geroulakos said: 'They were of all ages because DVT can affect all of us. Airlines should stop being in denial over the clear risk of flying.'
One of his patients gave evidence to the Lords inquiry, which was chaired by Baroness Wilcox and Lord Winston.
Their report on air travel and health will call for more research and point to new evidence that firstclass and Business class passengers are also at risk.
DVT kills 30,000 people a year in the UK, many due to high-risk factors such as heart disase, smoking and immobility. Other known risks include pregnancy and taking the Pill, but there are no definitive figures for the numbers who die after air journeys.
Medical experts suggest taking an aspirin before the flight, trying to book an aisle seat to make stretching easier, taking regular walks, drinking plenty of water and avoiding coffeine or alcohol.
Last night British Airways said it was too soon to comment on Mr Scurr's study, but added: 'We do know that immobility is one of many factors which can lead to blood clots. We inform our passengers through our health website and suggest exercises in our in-flight magazines to encourage them to move around.'
Virgin Airlines said it had a medical team working on the problem, but it was difficult to gauge the right response until medical research unanimously confirmed a link between flying and blond clots.
But Charter airline Britannia has started making announcements urging passengers to at least stand up occasionally and to move around when possible. It is sending all cabin Crews an DVT awareness courses.
Millions of passengers arrive in Britain each year on long haul flights. Inevitably, some will form an unrelated deep vein thrombosis in the days after their flight - just as some will be run over by buses, win a small lottery prize or come down with chicken pox. But doctors are increasingly concerned by anecdotal evidence of otherwise healthy passengers suffering from DVT.
They also suspect that the cramped conditions of a jumbo jet could be the final straw for patients already at risk - particularly those who smoke, overeat, have recently had an operation, are taking the contraceptive pill or who are receiving hormone replacement therapy.
In October 2000, Emma Christoffersen, a 28-year-old from Gwent, collapsed in the arrivals hall minutes after stepping off a 20-hour flight from Australia to Britain. Tests showed that Miss Christoffersen, who had been fit and healthy, had died from DVT.
In November last year, Thomas Lamb, 68, from Cardiff, complained of breathing difficulties a day after flying from Melbourne to Britain. He went into a coma five days later and died from a pulmonary embolism - a blood clot that had travelled to his lungs.
Last week, Susan Mavir-Ross, 42, from Llay, Wrexham, died following a nine-hour flight from San Francisco to Heathrow. Mrs. Mavir-Roll was travelling in business class and was treated on the plane by a doctor.
Eamonn Toland suffered a deep-vein thrombosis in his leg after flying to Hong Kong and back in a weekend. He collapsed shortly after landing in London but recovered.
DVT often begins in the calf or thigh because blood moves relatively
slowly in these areas, particularly if exercise is limited. As the blood
begins to pool in an area, a clot develops and can attach itself to the
wall of a vessel or in more severe cases become wedged within a vessel,
blocking blood flow. Blood clots are common. And while a blood clot itself
is not life threatening it can cause serious complications. Professor
Reginald Lord, head of the vascular group of St. Vincent's hospital in
Sydney, says only one percent of venous thromboses cause complications.
As a clot develops in size, it can shed pieces of the clot. These are
referred to as emboli. The emboli float through the blood system and can
travel through the heart to major arteries in the lung causing serious
and sometimes fatal complications.
One of the most serious is referred to as a pulmonary embolism where blood
flow to the lung is blocked. In rarer cases, the clot could also be pumped
towards the brain and block arteries that supply the brain. If this happens,
a potentially fatal stroke may result.
- Chest pain
- Pain in the calf or leg
- Swelling of the leg or lower limb
- Shortness of breath
- Surface veins becoming more visible
But often there are no symptoms at all. Only half of patients diagnosed with DVT had symptoms. According to David Grosser, a vascular surgeon in the Gold Coast, Australia, clots behave in many different ways."Patients can have a significant clot floating around unattached or have end bits that are the size of your thumbprint. Some can be a couple of feet long attached by a tiny little area. In examples like these there can be no symptoms and often these can be the most lethal," Grosser says.
Professor Lord agrees that identifying symptoms is difficult, particularly in severe cases.
"One of the commoner causes of sudden death is a pulmonary embolism that may occur a week to ten days later after a thrombosis formed," Lord says.
Diagnostic ultrasound is the best method to detect restrictions in blood flow, often in combination with blood tests. Diagnostic ultrasound is the best method to detect restrictions in blood flow, often in combination with blood tests. Treatment sometimes requires hospitalization to dissolve the clot and try and reduce the risk of other clots developing. The main treatment is blood-thinning medication administered intravenously and orally.Exercise also stimulates blood flow.
"Nature sends out a lot of signals. If you have been sitting in one position that the body doesn't like, you will feel cramped. That's the body telling you to change position or get up and move about," he says.
In relation to air travel, he advises those more at risk of developing DVT to begin taking half an aspirin a day for 10 days prior to travel. Medical professionals also recommend seeking medical advice before travel and during the flight to wear special compression socks and drink lots of water. But Professor Lord admits there are a number of factors associated with air travel that need researching and may increase the risk of DVT.
"Airline cabins are generally pressurized at 6000 feet. This may have an adverse effect on the endothelial cells [the cells lining blood vessels]. If damaged, that's often the beginning of the clot," he says.
"And at the end of a long flight, people have swelling in their feet and often can't put their shoes back on. The dynamics in flow has been altered. Fluid going up through the legs is passing out through local tissue. This could also be effective in increasing the risk."
http://www.cnn.com
Researchers findings (...): Simon found 59% of blood clot injuries attributable to air travel. Brown found 50%. Benoit 50%. Eklof 20%. Nissen 5%. A new study not yet published found 13%. Ferrari found air travelers have four times greater risk of blood clot injury. Scurr found 10% of air travelers developing clots, most of which would resolve naturally and not need treatment, but a small percentage causes leg or lung injury. A small percentage of 600 million air travelers is a lot of victims. The clots usually form in the calf (Deep Vein Thrombosis, DVT) when blood pools in the veins. Muscle activity is needed to pump venous blood back to the heart. An inactive or sleeping airline passenger fails to pump the blood. Clots may cause swelling and pain and can even lead to loss of the leg. If a clot breaks loose and travels to the lung (Pulmonary Embolism, PE) it can cause shortness of breath, pain, fainting, and sudden death. Often fainting is the first sign. Pain is not a reliable indicator; the largest and most dangerous pulmonary embolisms occur in an area where no pain is felt. Only small clots at the perimeter of the lung cause pain. (...)
ECS is a misnomer because while cramped economy class seating may increase the risk, flight related thrombosis strikes first class passengers and pilots as well. A more appropriate name would be Air Travel Syndrome to include all classes of passengers plus pilots and deadheading flight crews.
Stealth factor: symptoms of pulmonary embolism usually do not appear until a few days or more after the flight. Most victims have no idea what is happening to them. They suffer needlessly. Medical studies focussing only on people stricken at airports have been missing most of the victims. Compounding this is the fact that pulmonary embolism is, more often than not, misdiagnosed as heart attack, chest cold, or other conditions. Many victims die for lack of correct treatment. And the medical studies ignore still more of the victims, whose hospital records and death certificates say "heart failure". You can avoid getting a blood clot by doing the simple exercises we suggest. And if you still get one anyway, the information here will save you from needless suffering and misdiagnosis.
If you or a family member have suffered from thrombosis or pulmonary embolism after air travel please be sure to sign in at our membership page to help document the number of cases.
http://www.airhealth.org