Dr. Cushman explained how blood clots develop: “The veins are bringing blood back to the heart after arteries have given oxygen and nutrients to the tissues. It’s particularly difficult for the veins in the legs to do their job, because they have to bring the blood up against gravity.” The body relies on leg muscles to push the blood back from the legs to the heart, says Dr. Cushman. If the legs are immobile for hours at a time, the blood can begin to clot, leading to venous thromboembolism (VTE). Though there are other risk factors for VTE—surgery, traumatic injury, cancer—simply sitting for extended periods can be a primary cause. These are the silent signs of a blood clot you should never ignore.
When a clot moves or a section breaks off, the results can be fatal: It can travel to the brain causing a stroke; make sure you know what to do if you suspect a stroke. A clot can also lodge in the lungs, leading to a pulmonary embolism which can also be deadly. VTE affects between 300,000 and 600,000 people in the U.S. every year, making it the third leading vascular diagnosis after heart disease and strokes, yet according to Dr. Cushman, worldwide awareness is “low.”
To detect the impact of prolonged sitting, Dr. Cushman’s team tapped data from the Atherosclerosis Risk in Communities Study, which followed 15,000 middle-aged people (45-64 years old) for 20 years. They looked at the incidence of VTE and how it related to the volunteers’ TV-watching behaviors.
Scientists consider that TV habits are a good way to judge whether or not someone is living a sedentary lifestyle. Sure enough, the data revealed that people who watch TV “very often” had 1.7 times the risk of suffering a life-threatening blood clot compared to people who said they seldom or never watched the tube. To the researchers’ surprise, they found that even frequent TV watchers who exercised regularly were still 1.8 times more likely to get a blood clot than exercisers who rarely watched television.
“You can be physically active and also have sedentary behavior,” said Dr. Cushman. “They aren’t just opposites. People who are physically active don’t necessarily have low sedentary time.” In other words, regular exercise is important for many health reasons, but it’s not enough in itself. We also need to remain active throughout the rest of the day.
Content continues below ad
Dr. Cushman advocates limiting the amount of time we spend sitting, which includes any prolonged periods such as working at a desk or taking a long flight. “Do your 30 minutes of moderate exercise every day,” she said, “And then if you want to sit and watch TV for three hours at night, you should be moving during part of that time at least.” Dr. Cushman walks on a treadmill while watching TV and uses an hourly alert on her Apple watch to remind her to get up and move around regularly while she’s working.
She also has two pieces of advice to help avoid the dangers of VTE: “Number one is to educate yourself about this disease,” she said. ” When you are not aware, you can actually die because you don’t get treatment early enough.”
Symptoms of DVT include pain or tenderness in your calf or thigh, leg swelling, redness, and skin that feels hot to the touch. (Check out these other silent signs of DVT). A pulmonary embolism causes unexpected shortness of breath, rapid breathing, chest pain, increased heart rate and lightheadedness. This indicates the blood supply to the lungs has been cut off—which can be fatal. Recognizing the symptoms and seeking medical help urgently could make all the difference to your chances of survival. The American Heart Association has more detailed information and advice about VTE.
Although VTE most commonly affects those over the age of 60, establishing good habits when young will reduce your chances of developing a host of chronic conditions like heart disease and strokes later in life.
Dr. Cushman’s second piece of advice is clear: “Keep moving to have a healthy lifestyle. That involves not being sedentary, getting the recommended physical activity, and eating a healthy diet, which will help prevent this disease as well as almost every other chronic disease. These are the key things about preventing disease and maintaining a healthy long life.”