TUESDAY, July 5, 2011 (HealthDay News) -- Women who sit for long periods of time on a regular basis have a two- to threefold increased risk of developing a potentially deadly blood clot in their lungs, a new study finds.
The researchers said their study is the first to prove that an inactive lifestyle increases the risk of developing a pulmonary embolism, which occurs when part or all of a blood clot that forms in the deep veins of the legs travels through the bloodstream to the lungs.
Sudden shortness of breath, severe chest pain and coughing that may produce blood are among the symptoms of pulmonary embolism, in addition to excessive sweating, fainting and weak pulse.
The new study included 69,950 female nurses who were followed for 18 years and every two years provided details about their lifestyle habits. Women who spent most of their time sitting (more than 41 hours a week outside of work) were two times more likely to develop a pulmonary embolism than those who spent the least time sitting (less than 10 hours a week outside of work).
The link between levels of physical activity and pulmonary embolism risk remained conclusive after accounting for such factors as age, smoking and body mass index (a measurement based on height and weight), the researchers said.
The investigators also found an association between physical inactivity and high blood pressure and heart disease, which suggests that physical inactivity could be one of the hidden mechanisms that connect arterial disease and venous disease.
Public health campaigns that encourage people to be physically active could reduce the incidence of pulmonary embolism, concluded study author Dr. Christopher Kabrhel, attending physician in the emergency medicine department at Massachusetts General Hospital, and colleagues, in a statement.
Their study was published online July 4 in the BMJ.
The findings reinforce "the notion that prolonged inactivity increases the risk of venous thromboembolism [pulmonary embolism or deep-vein thrombosis], and it shows how this occurs in everyday life," Dr. James Douketis, director of vascular medicine at McMaster University in Hamilton, Ontario, Canada, and colleagues wrote in an accompanying editorial.
Although the risk is small -- equal to seven extra cases per 10,000 person-years -- the results could have major public health ramifications, the editorialists noted.
The study offers "additional evidence to prove what we've already seen in other contexts," Dr. Furqan Tejani, director of advanced cardiovascular imaging the State University of New York Downstate Medical Center in New York City, said in an e-mailed statement.
"For instance, Olympic athletes who took trips from Europe to Australia were found to have deep venous thrombosis and pulmonary embolism. Recently, in fact, one of the Williams sisters [tennis star Serena Williams] also had pulmonary embolism," Tejani noted.
"Whether travel and prolonged sitting had anything to do with it is not clear, but because a mounting body of evidence pointing to the fact that it may be, it is recommended that one take a baby aspirin before long-haul travels described as lasting more than eight hours," Tejani added. "Certainly it is recommended to at least get up and walk around the aircraft cabin and do calf muscle exercises on a regular basis while en route."
The U.S. National Heart, Lung and Blood Institute has more about pulmonary embolism.