Lead author Dorothy Dunlop, a professor of medicine at Northwestern University's Feinberg School of Medicine, said the study is the first to show sedentary behavior is its own risk factor for disability, separate from lack of moderate vigorous physical activity. In fact, sedentary behavior is almost as strong a risk factor for disability as lack of moderate exercise.
"This is the first time we've shown sedentary behavior was related to increased disability regardless of the amount of moderate exercise," Dunlop said in a statement. "Being sedentary is not just a synonym for inadequate physical activity."
For example, if there are two 65-year-old women, one sedentary for 12 hours a day and another sedentary for 13 hours a day, the second one is 50 percent more likely to be disabled, the study found.
"It means older adults need to reduce the amount of time they spend sitting, whether in front of the TV or at the computer, regardless of their participation in moderate or vigorous activity," Dunlop said.
The study focused on a sample of 2,286 adults age 60 and older from the National Health and Nutrition Examination Survey. It compared people in similar health with the same amount of moderate vigorous activity. Moderate activity was defined as walking briskly, as if late to an appointment.
The participants wore accelerometers from 2002 to 2005 to measure their sedentary time and moderate vigorous physical activity.
The findings were published in the Journal of Physical Activity & Health.