Especially for those over age 50.

By Amanda MacMillan
Updated August 30, 2017

You already know that sitting for prolonged periods is bad for you. But despite all the studies published on this topic, a new one still manages to paint a startling picture of the consequences of sedentary behavior—especially for adults 50 and up.

Older adults who reported watching more than five hours of television per day were 65 percent more likely to have difficulty walking (or be unable to walk) almost 10 years later, compared to those who watched less than two hours per day. The study, published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences, alsosuggests that extended TV time is especially dangerous for people who don’t get much physical activity throughout the week.

The study included more than 134,000 participants, who were taking part in a national research project sponsored by the National Institutes of Health and AARP. At the start of the study, all participants were between 50 and 71 years old, and were all in good health. They answered questions about the total time they spent sitting, watching TV, and participating in light and moderate-to-vigorous physical activity.

After 10 years, the participants were surveyed again, this time about their walking speed and gait. Anyone who reported walking at less than 2 miles per hour, or being unable to walk at all, was considered to have a mobility disability. About 30 percent of the original sample met these criteria.

First the good news: The researchers found that, for people who got more than seven hours a week of physical activity (the highest level recorded in the study), sitting for up to six hours a day was not a predictor of excess disability a decade later. Even people who sat for seven or more hours a day—but got seven-plus hours of exercise a week—still had significantly lower odds of being disabled compared to those who sat less but also got less activity.

But for most people in the study, too much sitting was a harbinger of bad things to come. And watching at least five hours of TV a day was associated with greater disability at follow-up, no matter how much physical activity people got the rest of the time. This was true even after the researchers controlled for other factors known to affect disability risk.

More than three hours of TV a day coupled with less than three hours a week of physical activity was the worst combination, and raised people’s risk of disability more than three-fold compared to those who watched the least TV and got the most exercise.

These findings are seriously worrisome, says lead author Loretta DiPietro, PhD, chair of the department of exercise and nutrition sciences at the George Washington University’s Milken Institute School of Public Health. DiPietro says that older adults are more susceptible to the health effects of physical inactivity, and that watching hours of television every evening is likely “one of the most dangerous things older people can do.”

“Young people can get away with it more because they have what we call physiologic reserve or robustness,” says DiPietro. “They can counteract 10 or 12 hours of sitting with a 45-minute to an hour-long vigorous workout. But as you age you lose some of that reserve, and so prolonged sitting becomes even more and more damaging.”

Watching TV at night seems to be an especially dangerous version of sedentary behavior, she says, because it involves so little movement. Even at a desk job during the day, she points out, people are often standing up or moving around, walking to the cafeteria or the bathroom, and attending meetings. It’s easier to zone out completely—and not get up for hours—while binge-watching your latest Netflix obsession, she says.

“And let’s face it, a lot of that sitting in front of the television is done in a recliner,” says DiPietro. “As you get older, it’s harder to get up and out of that position. Once you’re in it, you’re in it for a while.”

DiPietro says the best thing people can do at any age—but especially as they get older, and especially in the evening when it’s tempting to veg out for hours—is to move less and sit more. “Both of those are important,” she says. “And break up sitting time with walking around, climbing stairs, marching in place during commercials—anything you can do just to move more and sit less.”