Researchers in New Zealand have warned that long hours sitting in front of a computer screen could cause deep vein thrombosis (DVT), a condition that has been linked with long-haul flights.

Researchers at the New Zealand Medical Research Institute have reported what could be the first known case of "e-thrombosis" in a 32-year-old man who spent between 12 and 18 hours a day working at his computer. He came close to death after developing a massive blood clot that formed in his legs and travelled to his lungs.

Richard Beasley, director of the institute, said the incident may be the first reported case of "prolonged mobility sitting at a computer" leading to the development of life-threatening blood clots.

"He would typically sit for one to two hours, and not infrequently as many as six, without standing up from his work station," the researchers said.

"This certainly wasn't an isolated case," Mr Beasley said following his report's publication in the European Respiratory Journal. "Just as with deep vein thrombosis suffered by travellers, this was only recognised as a fairly large scale problem after the first few cases were publicised."

Mr Beasley has also led a team of New Zealand researchers investigating "economy class syndrome", or DVT linked to long-distance air travel.

DVT is a condition in which a blood clot forms in the deep veins of the legs. It can be fatal when part of the clot breaks off and blocks a blood vessel in the lungs.

Currently two airlines are participating in pilot studies being conducted by the World Health Organisation to determine whether or not flying can cause DVT. The results are not expected until 2007.

In Australia, 2,700 passengers are seeking damages from airlines after developing clots. Victims and their families are currently appealing a decision that prevented them from suing airlines in Britain. Cases are also working through the legal systems in Canada and the United States.

Research published in the medical journal Lancet in May found that about one in 10 people who took a long haul flight without wearing compression stockings developed a blood clot in their calf veins. The same researchers reported that wearing compression stockings appeared to negate the risk.