Sitting at work 'doubles the risk of DVT'

Their study, published in the Journal of the Royal Society of Medicine, involved 97 patients under the age of 65 attending a hospital outpatient clinic in New Zealand. All had previously been admitted to hospital with deep vein thrombosis (DVT) or pulmonary embolism (PE).

DVT is a blood clot in the legs or thighs while pulmonary embolism is a highly dangerous clot in the lungs. The term venous thromboembolism (VTE) is often used to cover both DVT and pulmonary embolism.

The patients were interviewed about their lifestyle and work pattern along with a comparison group of 106 others who had not been treated in hospital for clots. Prolonged sitting at work was associated with a two-fold increase in the risk of developing VTE.

People who spent large amounts of time in front of a computer should do frequent leg and foot exercises, and take regular breaks away from their desks, the researchers said.

Professor Richard Beasley from Wellington Hospital in New Zealand, who led the study, said the research mirrored investigations into the danger of blood clots on planes.

"It is similar to the situation with the risk of blood clots with long distance air travel," he said. "It was not until there was research into its role that the real extent of the problem was appreciated."

SIT syndrome

Professor Beasley stressed that the absolute risk of getting a blood clot was small. Other studies had found a DVT and PE rate of around 1.5 cases per 1,000 adults each year.

The development of blood clots after prolonged immobility caused by travel, work or other situations is known as SIT (seated immobility thromboembolism) syndrome.

SIT was first recognised during the World War II blitz on London. A number of people who spent long periods of time sitting in air raid shelters escaped the German bombs, but died of pulmonary embolism.

Two years ago research published by the Department for Transport (DfT) showed that people travelling long distances were exposed to a small, but increased risk of developing DVT and PE, regardless of the type of transport used.

The report concluded that travelling for more than 4 hours, whether going by plane, car, train or bus, port led to a threefold increase in the risk of VTE.

An abstract version of the Journal of the Royal Society of Medicine report can be found here.