Computer users risk blood clots

People who sit for hours in front of a computer may be at risk of developing blood clots in their legs, a study suggests.

The condition has been associated with long-haul air travel but a paper published in today's New Zealand Medical Journal, suggests sitting still for long periods at a computer could also cause deep vein thrombosis (DVT).

The researchers, led by Professor Richard Beasley of the Medical Research Institute of New Zealand, have proposed the acronym "SIT" - seated immobility thromboembolism - to cover all forms of seated immobility associated with DVT.

But they caution that the link between sitting still and developing a DVT in the five case studies investigated could be coincidental. Further research is planned.

The Wellington study was based on five people discharged from hospital with a diagnosis of DVT, who had a history of sitting for long periods and no other risk factors, such as recent surgery.

It found the subjects spent eight to 15 hours a day sitting for work and recreation - the maximum number of hours seated was 30 hours. The subjects, aged 24 to 39, included a computer worker, graphic designer and a chef, who spent much of his free time at a computer. The subjects reported sitting for between three to six hours without getting up.

"The likelihood of a young adult without underlying risk factors developing a DVT or pulmonary embolism would be considered to be extremely low, suggesting the importance of immobility as a provoking factor in these subjects," the researchers said.

Professor Beasley first reported the possible link two years ago in a study published in a European medical journal.

He said yesterday the problem had been around for many years but had been slow to be recognised. During World War II people who sat on deck chairs in underground shelters for long periods suffered from blood clots.

More recently a tall woman sitting in a cramped seat at a New Zealand movie theatre watching The Lord of the Rings suffered DVT. He said there was no need for people whose work involved sitting for long periods to panic.

Those who stood up and moved around, even wiggling their legs as they sat, were unlikely to be at risk.

"But if you are the person who sits at a computer five hours at a stretch without getting up, who is absolutely absorbed by the computer and does that on a regular basis, I think you are at risk."

Dr David Black, a senior lecturer in occupational medicine at Auckland University, welcomed the study and said it warranted further research.

Occupational Safety and Health standards recommended people get up and walk around every hour to try to prevent conditions such as occupational overuse syndrome.

Dr Black said the research further highlighted the need for people who had surgery - one of the groups at risk of DVT - to get mobile as soon as possible.

Dr Tricia Briscoe, chair of the New Zealand Medical Association, said more people were spending longer periods on computers and it was vital that activity that involved prolonged sitting was regularly broken by getting up and exercising the legs.

Professor Beasley hoped the study would raise awareness - in four of the five case studies prolonged sitting had not been recognised by attending doctors as a possible cause.