Researchers used an accelerometer (such as those found in a Fitbit or Apple Watch) to measure physical activity. Participants were asked how often in the past week their sleep was restless. Their responses could be “rarely” for less than one day, “some” for one or two days, “much” for three or four days, and “most” for five to seven days.
Some 300 people, or 16 percent, reported restless sleep three or more days in the past week. Participants who reported restless sleep for much or most of the time had 11.9 percent and 23.7 percent fewer weekly minutes of moderate-vigorous activity, respectively, compared with participants reporting that it was rare for them to have restless sleep. The deficit in activity remained even after accounting for age, gender, race, body mass index, other medical issues, and the severity and pain of their KOA.
People living with knee osteoarthritis have similar issues as people with other types of arthritis, says Dr. Gilbert. “These are patients with a lot of chronic pain, a lot of sleeping difficulties, and a lot of restless sleep,” she says. “Arthritis and the pain that comes with it influence the way people sleep, and their sleep influences the way they are physically active.”
“This study makes an important distinction about restless sleep; people don’t always consider restlessness and how it impacts sleep, and it’s important to consider,” says Rafael Pelayo, MD, a clinical professor of psychiatry and behavioral sciences at the Stanford Center for Sleep Sciences and Medicine in California. He found the number of people who experienced restless sleep in the study to be surprisingly small. “The people who reported the much to most amount of restless sleep was 16 percent, which seems low. In my experience, I would expect it to be higher than that,” he says, adding that the authors may be underestimating the severity of the problem of restless sleep by relying on self-reporting rather than another method, such as asking a bed partner.
What comes first, the chicken or the egg? Or to put it another way, which issue is leading the result here — that is, do people not exercise because they are too fatigued from poor sleep or do people not sleep well because they aren’t moving their bodies enough? “This is preliminary research — this needs to be looked at more closely to tease out this relationship and discover which is the chicken and which is the egg,” says Gilbert.