Researchers know that sedentary behaviors, such as spending long hours seated at a desk, can contribute to developing cardiovascular disease — even if people are otherwise active and eating healthy. But do all sedentary behaviors pose the same risk, or are some worse than others? A new study from the School of Public Health looked at an array of sedentary acts and found that when it comes to developing cardiovascular disease, watching TV may be the riskiest of them all.
The study, lead by researcher Kara Whitaker, was recently published in the American Journal of Epidemiology.
Whitaker found the link to TV watching by surveying the sedentary behavior of more than 3,000 people participating in the Coronary Artery Risk Development in Young Adults (CARDIA) study. In particular, she examined the time they reported spending watching TV as well as using the computer, doing paperwork, reading, talking on the phone, and sitting in a car. Whitaker also looked at each participant’s cardiovascular health indicators, such as blood pressure and cholesterol levels, to create a composite cardiovascular disease risk score.
She then compared the sedentary activity of the participants to their risk scores.
“What we found is that watching high amounts of television has the strongest association with increased cardiovascular disease risk out of all the sedentary behaviors,” says Whitaker. “On average, people in this study watched 2.2 hours of television per day.”
Overall, most of the sedentary behaviors were linked to increased risk, but TV viewing was found to be the highest. The study also showed that if participants replaced two hours of TV viewing with one of the other sedentary tasks, their disease risk went down.
“With reading or doing paperwork you have some movement, which could have a physiological benefit,” says Whitaker. “But with watching TV you can do it by moving nearly zero muscles — all you really need to do is blink and breathe.”
Whitaker speculates that the link between TV watching and cardiovascular disease risk could be from a tendency to snack on unhealthy foods during the activity. It is also possible that television advertising for unhealthy foods could prime people to later make less nutritious diet choices. Lastly, people who are depressed — which is linked to cardiovascular disease risk — often watch increased amounts of TV.
According to Whitaker, the findings establish a link between television viewing and cardiovascular disease risk, but don’t explain it, and so, more research is needed.
That said, Whitaker says that a broad takeaway health message is simple and clear:
“Try to reduce your sedentary behaviors, but in particular, everyone should limit their television viewing.”
Whitaker is now conducting related research examining the effects of replacing sedentary behavior with light-to-vigorous intensity physical activity on cardiovascular disease risk.