A study found that a third of patients admitted to a hospital with deep vein thrombosis (DVT) had jobs that involved sitting still at desks for long periods.

Office workers who spend all day sitting in front of computers may be at greater risk of developing potentially fatal blood clots than passengers on long-haul flights, according to new research carried out in New Zealand.

DVT is the formation of a blood clot in a deep vein, most commonly in the legs. The clots can travel to the heart, lungs or brain, causing chest pain, breathlessness or possible death from a heart attack or stroke.

DVT affects around 100,000 people and kills between 500 and 1,000 in Britain each year. Passengers sitting on long-haul flights without space to stretch out were considered as most at risk.

But Prof Richard Beasley. of New Zealand's Medical Research Institute, found that a third - 34 per cent - of 62 patients aged under 65 admitted to a hospital with blood clots spent long periods of time seated as part of their jobs. This compared to 21 per cent who had recently travelled on a long-haul flight.

"The risk is certainly there," he said. "There are considerably more people who are seated for long periods at work as part of their normal day than there are travelling."