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Regular Movement Essential for Circulatory Health

Prolonged sitting, such as during long car rides and airplane trips, has been known to trigger problems with blood clots, and now there is evidence that prolonged sitting at work is no exception. A new study found that people who sit for extended periods of time at work have an increased risk of a clotting problem known as venous thromboembolism (VTE).

The study, published in the Journal of the Royal Society of Medicine, included 203 people under 65 years old: 97 had been seen at the hospital for VTE and 106 had been to the hospital for other reasons. VTE involves the formation of clots in the veins that can become dislodged and travel to other parts of the body. Problems occur when the clots block blood flow, either in the vein where they form, as is the case in deep vein thrombosis, or when they travel to the lungs, as in pulmonary embolism.

Sitting at work raises the risk

People who reported a period of prolonged sitting at work in the four weeks prior to the onset of their symptoms were 80% more likely to have VTE. Prolonged sitting was defined as a 24-hour period that included eight hours of sitting and at least three hours without getting up, or, ten hours of sitting and at least two hours without getting up, or, 12 hours of sitting and at least 1 hour without getting up.

Both the maximum number of hours sitting at work during a 24-hour period and the maximum number of hours sitting at work without getting up were linked to risk of VTE. For every additional hour seated, the risk increased by 10%, and for every additional hour seated at work without getting up, the risk increased by 20%.

More sitting leads to more trouble

People in Western societies have been sitting more and more over the last century. “The history of prolonged immobility as a risk factor for VTE is intriguing,” the researchers said in the introduction to their report. “It was first recognized during the London Blitz in World War II, when the coroner’s pathologist reported a six-fold increase in the incidence of fatal pulmonary embolism occurring in people who sat for prolonged periods in air raid shelters.” In the 1950s, studies began to link VTE with other situations that involve prolonged sitting, such as car rides and air travel. Now the risk of VTE associated with travel is widely recognized as a public health issue, and this new study expands it to sitting at work.

“The fact that both the maximum number of hours seated at work and the number of hours seated at work without getting up increased the risk of VTE suggests that measures to reduce both of these factors may be important from an occupational health perspective,” commented study coauthor Professor Richard Beasley at the Medical Research Institute of New Zealand.

Remember to move

Based on the recommendations for people going on long air or car trips, people whose work involves prolonged sitting might reduce their risk of VTE by taking the following steps:

• Stay hydrated. Drink plenty of water and avoid over-consumption of alcohol and caffeine.

• Wear loose clothing that does not restrict the waist or legs.

• Flex and extend the ankles regularly while sitting to encourage blood in the veins of the lower legs to continue flowing.

• Stand up and move around at least once every hour, and try to restrict total sitting to less than eight hours per day.

(J R Soc Med 2008;101:237–43)

Maureen Williams, ND

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