Spending more than four hours a day sitting in front of a television or computer more than doubles your risk of dying from or being hospitalized for heart disease, according to a new study.

And even those who exercise can't overcome the detrimental effects of too much screen time, said study researcher Emmanuel Stamatakis, of the Department of Epidemiology and Public Health at the University College London.

Many people have sedentary jobs, and spend five to seven hours sitting at their desk or in their cars during their daily commute, he said. Tack on two to four hours of leisure time spent sitting, and the total can balloon to 10 hours a day spent parked in a chair.

"This is excessive," Stamatakis told MyHealthNewsDaily.

The study is published in the Jan. 18 issue of the Journal of the American College of Cardiology.

Death and risks

Stamatakis and his colleagues studied 4,512 adults who answered questions as part of the 2003 Scottish Health Survey. Researchers asked how much leisure screen time the people took in each day, which included watching TV or DVDs, playing video games and using the computer. After 4.3 years, there were 325 deaths from all causes and 215 cardiac events.

The researchers found that the people who spent more than four hours a day sitting in front of a TV or computer in their spare time were 48 percent more likely to die from any cause, and 125 percent more likely to have heart problems over the study period, than people who spent fewer than two hours of leisure time in front of a screen.

And exercise also didn't seem to neutralize screen time's effects on heart disease, Stamatakis said. There was no difference in heart disease risk between people who reported getting less than two hours a day of exercise and those who reported more than two hours a day of exercise, he said.

Causes and effects

Stamatakis said there are two reasons why spending leisure time in front of a screen might be associated with increased risks of dying and heart disease. One is that the type of person who sits in front of a TV for long periods of time may lead an unhealthy lifestyle in other ways as well.

Or, sitting for long periods of time could increase heart problems by inducing inflammation, he said.

Researchers found that blood levels of C-reactive protein — a marker of inflammation — was twice as high in people who spent more than four hours of time in front of a screen than people who spent less than two.

If it's true that the act of sitting is to blame, then "the findings are generalizable to those who sit and stare at a computer for eight hours a day during work," Stamatakis said.

The body needs to move around in order to break down sugars and triglycerides, said Dr. Gerald Fletcher, an American Heart Association spokesman and cardiologist at the Mayo Clinic in Florida, who was not involved with the study.

"Things are too convenient," Fletcher told MyHealthNewsDaily.

To add some movement into leisure time, he recommended ditching the remote control and getting up to change the channel on the TV, and keeping snack bars far away from the TV.

To increase physical activity at the office, he suggested using the bathroom or getting a drink of water on the other side of the office.

Pass it on: Spending more than four hours of your free time in front of a TV or computer each day increases your risk of death or hospitalization from heart disease twofold.

Follow MyHealthNewsDaily staff writer Amanda Chan on Twitter @AmandaLChan.