This article originally appeared on Health.com.
There’s a new way that watching too much television can be hazardous to your health: According to a study published today in the journal Circulation, it can increase your risk of dying from a blood clot in the lungs.
Sitting for long periods at a time is a risk factor for this type of dangerous clot, also known as a pulmonary embolism. In their study, Japanese researchers noted that pulmonary embolism occurs less frequently in Japan than in Western countries, but that it may be on the rise—and that increasingly sedentary lifestyles may be playing a role.
To test their hypothesis, from 1988 to 1990, the researchers asked more than 86,000 adults how many hours a day they spent watching television. Over the next two decades, 59 of those people died of a blood clot in the lung.
When they crunched the numbers, the researchers found that people who watched more than five hours of TV a day were 2.5 times as likely to have died from pulmonary embolism, compared with those who watched two and a half hours a day or less.
People who watched between two and a half and five hours a day were also at increased risk, although a significantly lower one (1.7 times, or 70% more likely). Overall, every two hours of daily TV watching over the baseline two and a half hours was associated with a 40% increased risk.
And that’s just counting people for whom pulmonary embolism was listed as the official cause of death on their death certificates, say the study authors. They estimate that the real risk is probably higher, because fatal pulmonary embolisms often go unreported or misdiagnosed. (Their main symptoms, chest pain and shortness of breath, can also be signs of heart attacks and other serious conditions.)
These study findings may be particularly relevant to Americans, especially since the advent of online streaming and the ability to “binge watch” multiple episodes in one sitting. Previous research has shown that adults in the United States tend to watch more television than those in Japan.
Anyone who watches a lot of television should take precautions to reduce their risk of developing a blood clot, says corresponding study author Hiroyasu Iso, MD, PhD, professor of public health at Osaka University Graduate School of Medicine in Japan.
“After an hour or so, stand up, stretch, walk around, or while you’re watching TV, tense and relax your leg muscles for 5 minutes,” said Dr. Iso in a press release. (Clots tend to start in the legs or pelvis, but can break free and travel through the blood stream, lodging in small blood vessels in the lungs.)
Dr. Iso also added that drinking water may also provide some protection, and that maintaining a healthy weight will also likely reduce risk. In the study, obesity had the second strongest association with pulmonary embolism, after time spent watching TV.
The study controlled for factors such as diabetes, cigarette smoking, and high blood pressure. It did not, however, include hours spent streaming video on computers, smartphones, or tablets, since questioning began before these devices were common. The authors say that new studies should be done to determine how these new technologies affect pulmonary embolism risk.