Poor sleep, negative attitude amplify pain in knee osteoarthritis

A new study reports that patients with knee osteoarthritis (OA) who have poor sleep habits display greater central sensitization - an amplification of clinical pain. Findings published in Arthritis Care & Research, a journal of the American College of Rheumatology (ACR), further show OA patients who catastrophize - consumed by thoughts of pain - had increased central sensitization that was associated with greater clinical pain.

OA - a degenerative joint disease that causes pain and swelling of joints in the hand, hips, or knee - affects nearly 27 million Americans 25 years of age and older according to the Centers for Disease Control and Prevention (CDC). Further evidence suggests that roughly one third of older adults have knee OA, a leading cause of pain and disability worldwide. Researchers believe that central sensitization, which is a hypersensitivity to pain, may contribute to the clinical pain amplification in OA.

"Our study is the largest and most comprehensive examination of the relationship between sleep disturbance, catastrophizing and central sensitization in knee OA," said lead author Claudia Campbell, Ph.D. from the Department of Psychiatry & Behavioral Sciences at Johns Hopkins University School of Medicine in Baltimore, Maryland.

The current case-controlled study included 208 participants who were categorized into four groups: OA patients with insomnia, OA patients with normal sleep habits, healthy controls with insomnia, and healthy controls without a pain syndrome and normal sleep. Seventy-two percent of the participants were female. Participants completed sleep assessments, psychological and pain evaluations, and sensory testing.

Results show that the subjects with knee OA and insomnia had the greatest degree of central sensitization compared to the controls. The team found patients with poor sleep and high catastrophizing scores reported increased levels of central sensitization. In turn, central sensitization was significantly associated with increased clinical pain.

Dr. Campbell concludes, "While no causal processes may be determined from this study, our data suggest that those with low sleep efficiency and higher catastrophizing have the greatest central sensitization. Understanding the intricate relationship between sleep, central sensitization, and catastrophizing has important clinical implications for treating those with chronic pain conditions such as knee OA."

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This study was supported by grants from National Institutes of Arthritis and Musculoskeletal and Skin Disease (R01 AR05487 & AR059410 [Smith]) and the National Institutes of Health (K23 NS070933, CMC).

What Is Osteoarthritis?

Osteoarthritis, commonly known as wear-and-tear arthritis, is a condition in which the natural cushioning between joints - cartilage - wears away. When this happens, the bones of the joints rub more closely against one another with less of the shock-absorbing benefits of cartilage. The rubbing results in pain, swelling, stiffness, decreased ability to move and, sometimes, the formation of bone spurs.