New research out of the University of North Carolina (UNC) suggests that there is a strong relationship between poor sleep quality and less physical activity. The study, published today in Arthritis Care and Research, included 1,892 men and women between ages 45 and 79 who had knee osteoarthritis (KOA) or were at risk of developing it. According to the Arthritis Foundation, 1 out of every 2 adults will develop symptoms of KOA in their lives.

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Although other studies have shown a link between arthritis pain and sleep disturbances, the large association between restless sleep and physical activity was notable to the lead author of the paper, Abigail Gilbert, MD, an assistant professor of medicine at UNC’s Thurston Arthritis Research Center in Chapel Hill. “I anticipate that these findings would be relevant to other types of arthritis,” she says.

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The Prevalence of Osteoarthritis in the United States

According to the Arthritis Foundation, approximately 27 million Americans have osteoarthritis (OA), making it the most common chronic condition of the joints. OA is classified into two categories: primary and secondary.

Primary OA is considered normal wear and tear, and it is associated with aging. The average age of onset for primary OA is around 65 years old.

Secondary OA tends to come on earlier in life and usually has a specific cause, such as an injury, inactivity, or obesity. People with rheumatoid arthritis (RA) often develop secondary osteoarthritis.

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The Link Between Sleep and Activity May Be Even Greater Than Research Suggests

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.

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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.

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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.”

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What Is Restless Sleep? And How Does It Relate to Poor Sleep?

“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.

Exercise as Medicine for People With Arthritis and Restless Sleep

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.

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The Connection Between Exercise, Joint Pain, and Good Sleep

“I always encourage my patients to be physically active, to start with walking just 10 minutes a day and trying to move a little bit,” Gilbert says. “I’ve had several of my patients say they sense an improvement in terms of feeling like they can sleep better. When they start to sleep better, they can move better.” Looking at physical activity and sleep in terms of a paired relationship could help improve the likelihood of a successful physical activity intervention, she adds.

Movement Is Natural Medicine That Boosts Mood and Eases Pain

“Trying to think about exercise as medicine can be helpful,” suggests Gilbert. “Try to remind yourself that moving will help your mood improve. Your mood is definitely related to your pain as well.”

Depression serves as a mediator in the relationship between restless sleep and inactivity, she says. “Depression is definitely part of this cycle and part of this relationship,” she says, adding that more research is needed to try to understand the impact and dynamic at work.

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Pay Attention to Your Pain, Your Sleep, Your Activity Level — and Talk With Your Doctor

Although every person is different, there are some general practices that can help. “Try doing some breathing exercises,” Gilbert suggests, or refocus with some positive self-talk. “I have patients remind themselves that the pain, the restless sleep, and mood are all related, and more movement is part of what it takes to get better.” Start with small steps like 5 or 10 minutes of getting outside and walking around the block, she says.

How Well Are You Really Sleeping? How Much Rest Are You Getting?

Sleep is the other important half of the equation. “It’s also important to recognize when you’re not sleeping well and speaking with your physician about how to address it,” Gilbert says.

If you wake up feeling tired, take notice, says Dr. Pelayo. It may be an early warning that’s something is not going right. “If you find that no matter how much sleep you get, you’re still tired, that’s a problem. You shouldn’t pass that off as normal aging; let your doctor know,” he says. For something like OA, your doctor may want to improve your physical therapy or adjust your anti-inflammatories, he speculates. “If you tell your doctor that you’re tired, and he replies, ‘I’m tired, too,’ you may be going to the wrong doctor,” Pelayo says.