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by Jones P

Risk for Deep Vein Thrombosis May Be Increased With Prolonged Periods of Sitting at Desk

Deep vein thrombosis (DVT) is a blood clot that develops in a vein deep in the body. This clot can cause a backup in blood flow, causing pain and disability. If part of the clot breaks off it can also travel up to the lungs causing a pulmonary embolism (PE) which can be fatal. The clot can be formed because of slow blood flow, pooling of blood, injury, or clotting problems. Muscle contractions in the limbs help push blood through veins back to the heart. Long periods of immobility, like sitting at a job, increase the chance that a clot will form.
While long flights and bedrest have been studied, there have been few studies that specifically looked at the long hours of immobility at a desk. The Capital and Coast District Health Board in New Zealand wanted to investigate the possible link. The study, published in the Journal of the Royal Society of Medicine , found that the more hours spent seated at work the higher the risk for venous thromboembolism (VTE). PE and DVT result from VTEs.

About the Study

The study was a case-control study. Investigators reviewed 97 cases of people who had DVT or PE and a control group of 106 people with similar characteristics that did not have DVT or PE. People from both groups were given questionnaires about their VTE.
Their time spent sitting was split into total time spent seated and length of time before getting up. The investigators defined prolonged sitting as:
  • Seated at least eight hours a day and at least three hours at a time without getting up
  • Seated at least 10 hours a day and at least two hours at a time without getting up
  • Seated at least 12 hours a day and at least one hour at a time without getting up
They reviewed time seated at work itself and total time spent seated at work which included work, travel, and seated at a computer at home. Their analysis showed:
  • The maximum number of hours seated at work was associated with VTE, increasing 10% per hour longer seated
  • The number of hours seated without getting up was associated with VTE, with the risk increasing by 20% per hour longer seated
Case-control studies can provide preliminary information, but are generally not considered completely reliable. Further studies will need to be done to confirm this link and remove or control variables that can affect the outcome.

How Does This Affect You?

Many jobs may require long hours at a desk. Avoid spending long periods sitting without a break. Make a habit of getting up and moving once every hour. Take the stairs instead of the elevator when possible, walk to someone’s office instead of sending an e-mail, or take the long route to a meeting or lunch. These little breaks will help your muscles work as pumps and prevent blood from pooling in your legs.
If you have a clotting issue, talk to your doctor about appropriate medical treatments and lifestyle changes.


American Academy of Family Physicians
Orthopaedic Connection—American Academy of Orthopaedic Surgeons


West J, Perrin K, Aldington S, et al. A case-control study of seated immobility at work as a risk factor for venous thromboembolism. J R Soc Med . 2008 May;101(5):237-43.

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