Slumping in front of the TV every night after work can double the risk of deadly blood clots, a research suggests.
Experts found that sitting down for more than 41 hours a week outside of work increases the chance of suffering a blood clot in the lungs.
The study, on almost 70,000 women, found that those who sit for long periods are two to three times more likely to develop a clot than those who sit for less than 10 hours outside of work.
It is thought to be the first study of its kind to find a link between a sedentary lifestyle and pulmonary embolism.
But the researchers, writing in the British Medical Journal, do say the risk is small and is only slightly higher than that for people who fly long haul or women who take the Pill.
A blood clot can travel from deep veins in the legs into the lungs, potentially causing death.
Symptoms of a clot include difficulty breathing, chest pain and coughing.
Natasha Stewart, senior cardiac nurse at the British Heart Foundation, said: “We have to be slightly cautious about this research because it only focused on women over the age of 55, but it adds weight to what we already know – physical activity is great news for your heart and circulation.
“Sometimes, after a long day at work, all we want to do is put our feet up in front of the TV but we know that physical inactivity is linked to heart and circulatory disease.
“Lots of small changes can make a big difference though so try getting off the bus one stop earlier or sign up to a new active hobby with your family or friends.
“Combining at least 30 minutes of physical activity each day with other healthy lifestyle choices, including staying a healthy weight, eating a balanced diet and quitting smoking, will also help to protect you from developing circulatory disease conditions, such as pulmonary embolism, and keep you healthy.”
Meanwhile another report indicated that lying around for long stretches outside of work doubles the risk of dangerous blood clots in the lungs, according to a study.
Previous research has highlighted a number of factors for this condition, including age, immobility,obesity, smoking and hypertension.
The new research suggests that a sedentary lifestyle can be added to the list. Over the 18-year study period, there were 268 cases of pulmonary embolism.
Results held even after age, weight and tobacco consumption were taken into account.
Researchers called for further work to see if the results also applied to men, and to people not of European origin.
They also pointed out that the mean age of the women studied was 55, leaving open the question of whether younger women would be subject to the same risks.