Who hasn't started to watch a new drama series on TV, and suddenly realize that hours have slipped by as they binged on one episode after the next?
Now, a new study suggests that too much binge-watching may raise the risk of life-threatening blood clots in the legs or lungs by 35%.
"Prolonged TV viewing, which involves immobilization, may increase the risk of venous thromboembolism," said lead researcher Dr. Setor Kunutsor, a senior lecturer at the University of Bristol's Medical School, in the United Kingdom.
The findings apply to more than couch potatoes: Being physically active does not eliminate the increased risk of clots associated with prolonged TV watching, he said, so "individuals need to take breaks during prolonged TV watching."
Kunutsor cautioned that the study can't prove that binge-watching TV causes clots, only that the two may be connected.
For the study, Kunutsor's team pooled data from three previously published studies that included more than 130,000 participants. In this process, called a meta-analysis, the researchers looked for connections between TV watching and venous thromboembolism (VTE). VTE includes pulmonary embolism (a blood clot in the lungs) and deep vein thrombosis (blood clot in a deep vein, usually in the legs, which can travel to the lungs and cause a pulmonary embolism).
In a follow-up that ranged from five to 20 years, more than 900 participants developed VTE. Those who binge-watched the longest (four hours per day or more) were one-third more likely to develop blood clots than those who watched the least amount of TV or never binged. The association was independent of age, sex, body mass index (BMI) and physical activity, the researchers noted.
"We should limit the time we spend in front of the television," Kunutsor said. "Even if you want to binge-watch TV, you should intersperse it with regular movements to keep the circulation going."
And the link likely exists for any kind of prolonged sitting. For example, if your work involves working long hours in front of a computer, be sure to get up and move around from time to time, he advised.
"Also, increase your physical activity levels when you binge-watch TV, as high volumes of physical activity can reduce or may eliminate the risk of diseases such as venous thromboembolism, which are associated with sedentary behaviors," Kunutsor said.
The report was published Jan. 20 in the European Journal of Preventive Cardiology.
Dr. Mary Cushman, vice chair of medicine and co-director of the Vermont Center for Cardiovascular and Brain Health at the University of Vermont in Burlington, said it's not clear yet if this relationship is causal.
"But, for example, people who watch TV more might be more likely to be obese or overweight, and obese and overweight is an established risk factor for VTE," she said. But the studies adjusted for body weight and still found an association of prolonged TV viewing with VTE, which suggests that the findings hold regardless of body weight, Cushman noted.
"We know that people who tend to watch TV for prolonged periods of time are less physically fit, and this could explain the association," she said. "It is also possible that the prolonged sitting reduces blood flow up the veins from the legs, which can contribute to the VTE — slow-flowing blood likes to clot abnormally."
More research is needed, Cushman said, "but the bottom-line message is that if you like to watch TV for prolonged periods, interrupt this with frequent walks and stretching, watch from a treadmill, not a chair, and don't snack while you are watching."