Scientists are warning the general public to take breaks while watching TV, after a study found that binge-watching for four hours or more a day is associated with a 45% higher risk of blood clots compared to keeping your watch-time below 2.5 hours.

The study, published in the European Journal of Preventive Cardiology, examined the association between TV viewing and venous thromboembolism (VTE), including pulmonary embolism (blood clot in the lungs) and deep vein thrombosis (blood clot in a deep vein, usually the legs, which can travel to the lungs and cause pulmonary embolism).

Prolonged TV viewers were 1.35 times more likely to develop VTE

The researchers combined three studies in a meta-analysis, with a total of 131,421 participants aged 40 years and older without pre-existing VTE. The amount of time spent watching TV was assessed by a questionnaire and participants were categorised as prolonged viewers (watching at least four hours of TV a day) or never/seldom viewers (watching 2.5 hours or less a day).

The average duration of follow-up across the three studies ranged from 5.1 to 19.8 years, during which 964 participants developed VTE. When analysing the relative risk of developing VTE in prolonged viewers compared to never/seldom viewers, they found prolonged viewers were 1.35 times more likely to develop VTE.

All three studies adjusted for age, sex, body mass index (BMI) and physical activity since they are related to the risk of VTE. Lead author of the study Dr. Setor Kunutsor of the University of Bristol said: “The findings indicate that regardless of physical activity, your BMI, how old you are and your gender, watching many hours of television is a risky activity with regards to developing blood clots.”

The findings suggest we should limit time spent in front of our television

While Dr. Kunutsor noted that the findings are based on observational studies and do not prove that extended TV watching causes blood clots, he suggests that it is likely the immobilisation involved with TV watching that increases the risk of developing VTE.

“Prolonged TV viewing involves immobilisation which is a risk factor for VTE. This is why people are encouraged to move around after surgery or during a long-haul flight. In addition, when you sit in a cramped position for long periods, blood pools in your extremities rather than circulating and this can cause blood clots. Finally, binge-watchers tend to eat unhealthy snacks which may lead to obesity and high blood pressure which both raise the likelihood of blood clots,” he explains.

Dr. Kunutsor says that the findings suggest that we should limit time spent in front of our television, and if we find ourselves binge-watching, or sitting in general for a significant period of time, we should make sure to get up and move around from time to time to keep circulation going.