"Importantly, participation in exercise did not seem to mitigate against the harms associated with excessive screen times," Stamatakis said.
In addition, biology appears to play a role. For example, one-fourth of the link between screen time and heart attack was associated with levels of C-reactive protein, which is a marker of inflammation along with weight and cholesterol, suggesting that inflammation and high cholesterol, combined with sitting, may increase the risk for cardiovascular events, the researchers said.
One way to keep healthy is to limit the amount of time spent sitting, Stamatakis said. Start by watching less TV, which many people do three to four hours a day, he added.
"This is excessive," he said. "And besides, TV watching [is] a waste of time in the most passive and uncreative way, in most cases. It also displaces hugely beneficial physical activity and, according to our findings, is also linked to unique and distinct risks for health."
Commenting on the study, Dr. Suzanne Steinbaum, a preventive cardiologist at Lenox Hill Hospital in New York City and a spokeswoman for the American Heart Association, said that "what I like about this study is it helps us understand the significant role that a sedentary lifestyle has on the risk of heart disease."
"We are all so fixated during the workday on the computer, and sitting has become such a regular part of our lives, that if we choose to sit for leisure, it's really harmful for us," she said.
Steinbaum recommends doing something physical every day -- and not sitting when you don't have to. "Leisure activity should be something that helps get [you] moving, no matter what this is," she said.
The American Heart Association has more on preventing heart disease.
SOURCES: Emmanuel Stamatakis, Ph
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