Too Much Screen Time Means Health Decline More than four hours a day in front of a screen shortens your life, study says.

Jan. 11, 2011 -- David Herbin goes to the gym every day after work and exercises like a demon for two hours. Then he comes home, flops on the couch and watches sports until bedtime.

Actually, now that the NFL playoffs are in full swing, he's glued to the tube even more than usual, often up to four hours per game even when there are multiple games on per day including the weekends. Though his wife Pegine admits his prolific TV viewing sometimes drives her crazy, she can't argue with the fact that the 57-year-old is still in great shape.

Or can she? A new investigation reported in today's Journal of the American College of Cardiology (JACC) begs to differ.

According to the study conducted by a group of international researchers, anyone who devotes more than four hours daily on screen-based entertainment such as TV, video games or surfing the web, ups their risk of heart attack and stroke by 113 percent and the risk of death by any cause by nearly 50 percent compared to those who spend less than two hours daily in screen play -- and this is regardless of whether or not they also work out.

The researchers surveyed more than 4,500 Scottish adults to find out how much time they spent parked in front of a TV, computer or gaming screen when not at work. (Scottish work and recreation habits jibe with the rest of the modern Western world, including the "American idle".) Then they analyzed their medical records for four years to find out how many of them succumbed to health problems or died during that time period.

Dedication to couch potato-style recreation translated into a greater incidence of poor health even after allowing for factors such as physical activity, age, sex and smoking.

"Assuming that leisure-time screen time is a representative indicator of overall sitting, our results lend support to the idea that prolonged sitting is linked to an increased risk for cardiovascular disease and premature mortality," notes the report's lead author, Emmanuel Stamatakis of the Department of Epidemiology and Public Health at University College in London. "Doing some exercise every day may not compensate for the damage done during very long periods of screen time."

The Risk of Sitting Down

This study is the latest to build on a growing body of research that shows that we humans are not designed to park ourselves in front of a screen for extended periods of time without deleterious effects.

For starters, the number of calories expended during sitting is exceptionally low -- so low that simply standing and exerting some minimal effort like shifting your weight from side to side doubles metabolic rate. Many researchers speculate this is part of the reason why chronic sitters are especially predisposed to obesity.

Even engaging in 30 minutes of brisk walking a day -- the current physical activity recommendation by groups such as the American Heart Association -- doesn't come close to canceling out the slothfulness of a desk job where the average sedentary worker often sits for 10 or more hours per day.

According to Stamatakis, a long sit causes a dramatic reduction in the activity of a very important enzyme called lipoprotein lipase (LL) -- an up to 90 percent reduction when compared to standing and moving. Among other functions, LL is responsible for breaking down fat that circulates in the blood to make it available for the muscles to use as energy.

Reduced LL activity leads to higher levels of circulating fats such as triglycerides in the blood, which could explain some of the link between an inactive lifestyle and cardiovascular disease.

New evidence shows that lack of movement may also impair glucose metabolism, predisposing desk jockeys to type two diabetes as well.

"I would speculate that the list of sitting-specific health harms will be getting longer and longer in the years to come; this area of research is in its infancy," Stamatakis says.

And, while it's true that more and more people remain seated during the bulk of their working hours, this particular investigation only examined "recreational sitting" because, the researchers reasoned, it's discretionary and the most obvious place people can make changes in their lives.

Sports fanatics like Herbin, for example, could get at least some viewing time out of their systems by tuning into the game while jogging on the treadmill.

He might consider slowly pedaling a stationary bike while watching or standing for at least part of the time he's cheering on his favorite team. Avoiding the inevitable mindless screen eating can also help him stay slim and healthy.

Exercise Important in Countering Sedentary Life

Stamatakis adds that since modern life has moved to the sluggish end of the activity continuum we need to find ways to make moving and standing the default states and sitting the exception.

Even though a formal workout program didn't appear to offer protection from the ill effects in this study, Stamatakis still cautions that avoiding sitting is not enough to make up for lack of exercise; we should all still aim for a minimum of 30 minutes of physical activity daily.