Older people who watched more than five hours of TV every day and reported three or fewer hours of total physical activity per week had more than a three-fold higher risk of being unable to walk or having difficulty walking at the end of an eight-year study.
This study was authored by Loretta DiPietro, chair of the Department of Exercise and Nutrition Sciences at the Milken Institute School of Public Health. The study assessed all types of sedentary behavior, as well as light, moderate and vigorous physical activity. Dr. DiPietro observed that prolonged sitting and TV watching combined with reduced physical activity was particularly harmful.
“TV viewing is a very potent risk factor for disability in older age,” Dr. DiPietro said. “Sitting and watching TV for long periods—especially in the evening—has got to be one of the most dangerous things that older people can do because they are much more susceptible to the damages of physical inactivity.”
Dr. DiPietro and her colleagues analyzed data from the National Institutes of Health-AARP Diet and Health Study, which kept track of men and women age 50 to 71 from six states and two metropolitan areas. They analyzed data of all participants who were healthy when the study began in 1995-1996. The researchers recorded how much the participants watched TV, exercised or did gardening, housework or other physical activity at the beginning of the investigation.
They followed participants for nearly a decade, and at the end of the study, nearly 30 percent of the previously healthy participants reported a mobility disability—having difficulty walking or being unable to walk at all.
The researchers observed that:
- Participants who watched five or more hours of TV daily had a 65 percent greater risk of reporting a mobility disability at the study’s end, compared with those who watched the least amounts of TV (less than two hours per day). This association was independent of their level of total physical activity, as well as a variety of risk factors known to affect mobility disability risk.
- Increasing levels of total sitting and TV time in combination with low—three hours per week or less—physical activity were especially harmful, resulting in an acceleration of risk.
- Among those people in the most physically active group (greater than seven hours per week), total sitting of six hours per day or less was not associated with excess mobility disability.
- Within all levels of physical activity, increasing amounts of TV viewing time increased the likelihood of a walking disability.
Other studies have found that too much sitting is a health hazard even for older people who meet the moderate to vigorous intensity physical activity guidelines of at least 150 minutes per week. But unlike this study, previous research did not follow people prospectively over a long period of time and did not consider the combined impact of both sedentary time and physical activity.
Younger people might be able to get away with sitting for long periods because they are physiologically more robust, Dr. DiPietro said.
After age 50, however, this study suggests prolonged sitting and prolonged television viewing becomes particularly hazardous.
TV viewing in the evening may be especially detrimental to health because it is not broken up with short bouts of activity, compared with sitting during the day, Dr. DiPietro said.
“We’ve engineered physical activity out of our modern life with commuting, elevators, the internet, mobile phones and a lifestyle—think Netflix streaming—that often includes 14 hours of sitting per day,” Dr. DiPietro said. “Our findings suggest that older people who want to remain fit must ramp up their daily physical activity and reduce the amount of time they spend sitting.”
Dr. DiPietro suggests building more physical activity into daily life to reduce risk. People who sit for long periods in front of a computer should get up every hour or switch to a standing desk, she said. Commuters can park the car several blocks away from the office or decide to take the stairs. Older people should walk as much as possible throughout the day, and everyone should consider binging less on television, she said.
“To stay active and healthy as you age, move more and sit less—throughout the day—every day,” Dr. DiPietro said.
The study, “The Joint Associations of Sedentary Time and Physical Activity with Mobility Disability in Older People: The NIH-AARP Diet and Health Study,” was published Wednesday in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences. The work was supported in part by the National Institutes of Health, National Cancer Institute.
