People who watch a lot of television may have an increased risk of dying from a blood clot in the lungs, a new study has found.

Known as a pulmonary embolism, lung blood clots usually begin as a clot in the leg or pelvis. It the clot breaks free, it can travel and become lodged in the small blood vessel of a lung, which is extremely dangerous.

These types of clots are often associated with periods of inactivity, e.g. if a person is taking a long-haul flight. However, Japanese researchers have found that those who watch television for long periods each day are also at risk.

They monitored the progress of over 86,000 people aged between 40 and 79 over a 19-year period. They found that compared to people who watched television for less than two-and-a-half hours per day, deaths from pulmonary embolisms jumped by 70% among those who watched TV for between two-and-a-half and just under five hours.

Overall, the risk increased by 40% for each additional two hours of television watched per day and those who watched TV for more than five hours per day were 2.5 times more likely to die from a pulmonary embolism.

The researchers believe that the risk is probably greater than these findings suggest because such deaths are thought to be under-reported as diagnosis can be difficult. The most common symptoms are chest pain and shortness of breath, which can be confused with many other conditions.

The study took into account factors that may have influenced the findings, such as smoking, obesity and diabetes. After television watching was taken into account, the next strongest link appeared to be due to obesity.

"Nowadays, with online video streaming, the term ‘binge-watching' to describe viewing multiple episodes of television programs in one sitting has become popular. This popularity may reflect a rapidly growing habit.

"After an hour or so, stand up, stretch, walk around, or while you're watching TV, tense and relax your leg muscles for five minutes," the researchers said.

They noted that this advice is similar to that given to travellers on long-haul flights. They also pointed out that drinking water may he helpful and if you are overweight, you should try to lose weight.

Details of these findings are published in the journal, Circulation.