People who spent more than four hours a day doing light physical activity had more than a 30 percent reduction in their risk for developing a disability, compared to those spending only three hours a day in light activity, researchers found.
"The bottom line is to stay as active as possible. Even spending time in light activity will be beneficial," said lead author Dorothy Dunlop, a professor with the Center for Healthcare Studies at Northwestern University's Feinberg School of Medicine, in Chicago.
The federal government recommends that adults get at least 2.5 hours of moderate-intensity exercise a week. Such exercise is known to reduce a person's risk of disability, Dunlop said.
But some people have health issues that prevent them from pursuing that level of exercise, which includes activities like walking briskly, water aerobics, ballroom dancing and bicycling slower than 10 miles per hour, she said.
So researchers decided to see whether even lighter exercise could reduce a person's risk of becoming disabled due to a condition like knee osteoarthritis.
The study involved a group of almost 1,700 adults, aged 45 to 79, who were participating in a long-term study of osteoarthritis. The participants were all free of disability, but they were at elevated risk for becoming disabled due to knee arthritis.
Disability currently accounts for more than one of every four dollars spent on health care, the researchers said in background material. Nearly one in five people in the United States was classified as disabled in 2010, at an estimated annual cost of $357 billion.
These disabilities can severely affect a person's daily life, making it tough for them to perform basic tasks such as dressing themselves, taking a shower or even moving around their own home.
For the new study, researchers had the participants wear an accelerometer around one hip during their waking hours for about a week. The device measured the intensity of their daily movements, giving the study team an idea how much time they spent in vigorous, moderate or light physical activities.
Two years later, the researchers checked back in with the participants to see whether they had developed any disabilities.
The investigators found that people who frequently engaged in light physical activity were much less likely to become disabled, even after accounting for time spent in moderately intense exercise.
People who took part in more light activity were one-third to one-half less likely to suffer a disability, compared to people who had the least amount of daily light activity, the researchers noted.
Light physical activity also slowed the progression of people already suffering from a disability, the findings showed.
And while people who took part in some moderate-intensity exercise did even better, the researchers found, their results show that some movement is better than none.
"Our findings provide encouragement for adults who may not be candidates to increase physical activity intensity due to health limitations," Dunlop said. "Even among those who did almost no moderate activity, the more light activity they did, the less likely they were to develop disability."
The study appeared in the April 29 issue of the BMJ.
The findings correlate with what doctors often recommend to patients with osteoarthritis, said Dr. Elizabeth Matzkin, an orthopedic surgeon and surgical director of women's musculoskeletal health at Brigham and Women's Hospital, in Boston. She was not involved with the new research.
"We have always tried to recommend to our patients that physical activity is extremely important, and especially in our patients with early osteoarthritis," she said. "The most important thing they can do is self-management -- basically stay active through some sort of exercise, and keep their weight down."
Armed with this study, doctors can argue that even moving around your house to make a bed or wash some dishes will help stave off disability, Matzkin said.
"I tell my patients that you're going to be bad off if you do nothing, but there is a threshold for exercise and if you overdo it, you can hurt yourself and be worse off," she said. "This study definitely shows that if you get off the couch and do something, no matter how light, you're still going to reap some benefits."
For more about managing arthritis pain with exercise, visit the American Academy of Orthopaedic Surgeons.