A Preliminary Examination of the Effects and Mechanisms of Cognitive Behavioral Therapy for Insomnia on Systemic Inflammation Among Patients with Knee Osteoarthritis

Background: Systemic inflammation, particularly the elevation of interleukin-6 (IL-6), plays an important role in the maintenance and progression of knee osteoarthritis. Insomnia, being highly prevalent in knee osteoarthritis, is understood to be a risk factor for systemic inflammation. The present study examined if cognitive behavioral therapy for insomnia (CBT-I) would reduce circulating IL-6 levels to a larger extent than the active control condition via greater improvement in sleep maintenance disturbance at mid-treatment, among individuals with knee osteoarthritis and insomnia disorder.

Methods: This is an ancillary study (N = 64) from a larger double-blind, randomized, active controlled clinical trial. Serum IL-6 was measured at baseline, post-treatment, and 3- and 6-month follow-ups. Sleep was measured by daily sleep diaries.

Results: Overall, there was no significant IL-6 trajectory differences between CBT-I and the active control (p = .64). Compared to the active control, CBT-I demonstrated greater improvement in sleep maintenance disturbance at mid-treatment (p = .01), which, in turn, was significantly associated with lower levels of IL-6 at 3-month follow-up (p < .05). Sleep maintenance disturbance at mid-treatment did not significantly predict changes in IL-6 levels at post-treatment (p = .43) and 6-month follow-up (p = .90).

Conclusions: Our study demonstrates that CBT-I can be efficacious in improving sleep maintenance disturbance among individuals with knee osteoarthritis and insomnia disorder. However, no convincing evidence was found that CBT-I can substantially reduce IL-6 levels via improvement in sleep. CBT-I alone may not be effective in reducing systematic inflammation in this clinical population.

Trial registration: NCT00592449.