Sitting in a window seat of an aeroplane during long distance flights can increase the risk of deep vein thrombosis (DVT), doctors say.

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Sitting in a window seat of an aeroplane during long distance flights can increase the risk of deep vein thrombosis (DVT), doctors say.
A window seat is one of the risk factors for DVT in long distance travellers outlined in new guidelines by the American College of Chest Physicians (ACCP), which say that a person's individual risk factors for blood clots should be taken into account before being offered preventative medicines.
Other risk factors highlighted include being elderly, pregnant or taking oral contraceptives.
The experts also say that so-called '"economy class syndrome" is a myth, as the risk of developing a blood clot during a long haul flight is the same for those travelling in first or business class.
Deep vein thromboses are blood clots which usually develop in the legs. If a clot breaks away, it can cause a potentially fatal blockage in the lungs known as a pulmonary embolism.
The new guidance, published in the journal Chest, says the risk of developing a blood clot on a long distance flight is "very small" for most people, but was increased for flights taking longer than eight or ten hours.
Prolonged sitting, such as in a window seat of a plane, can also increase the risk of DVT, but particularly in people with other risk factors.
Guidelines co-author Dr Mark Crowther from McMaster University, Ontario, said: "Travelling in economy class does not increase your risk for developing a blood clot, even during long-distance travel.
"However, remaining immobile for long periods of time will. Long distance travellers sitting in a window seat tend to have limited mobility, which increases their risk for DVT. This risk increases as other factors are present."
Smoking and obesity were also identified as risk factors, but the doctors said they found no "definitive evidence" that either dehydration or drinking alcohol boosted the risk of DVT.
Medical conditions which can put a person at increased risk include having had recent surgery, a family history of blood clots and having heart disease.
The guidelines recommend that all long-haul passengers should take preventative measures such as getting out of their seats and walking around, and calf muscle stretches.
In addition to this, people at higher risk of DVT should sit in an aisle seat if possible and wear below-knee graduated compression stockings, they advised.
The doctors also advised against the use of aspirin or any other anti-coagulant medication to prevent DVT in long-distance travellers.
Drugs which can prevent blood clotting should only be considered on an individual basis for those at a higher risk of DVT as the "adverse effects may outweigh the risks," they said.
Dr Gordon Guyatt, who chaired the panel of experts which drew up the guidelines, said: "There has been a significant push in health care to administer DVT prevention for every patient, regardless of risk.
"As a result, many patients are receiving unnecessary therapies that provide little benefit and could have adverse effects."
"The decision to administer DVT prevention therapy should be based on the patients' risk and the benefits of prevention or treatment."