Objective: To determine the patient characteristics that are associated with a response to noninvasive placebo acupuncture for insomnia. Methods: We performed a secondary analysis of three randomized, double-blind, placebo-controlled trials of acupuncture for primary insomnia and residual insomnia associated with major depression. A total of 86 participants were randomized to receive placebo acupuncture three times per week for three consecutive weeks. Outcome was assessed at 1-week posttreatment. Response was defined as an Insomnia Severity Index (ISI) score improved by eight points or more from baseline to 1-week posttreatment. Sociodemographic, clinical, and baseline characteristics including sleep diary-derived and actigraph-derived sleep parameters as predictors of placebo response were examined using univariate and multivariate logistic regression. Results: The effect size of placebo acupuncture was estimated at 0.18 for total sleep time, 0.08 for sleep efficiency, and 0.92 for ISI score. Eighteen (20.9%) of the 86 participants were responders. Responders had a higher ISI score (p = 0.03), higher sleep diary-derived total sleep time (p = 0.02), less discrepancy between sleep diary-derived and actigraph-derived total sleep time (p = 0.03), and higher expectation toward acupuncture (p = 0.03) at baseline compared to nonresponders. Multivariate regression analysis found that only ISI score remained significant (odds ratio = 1.23, 95% confidence interval = 1.02-1.50, p = 0.03). Conclusions: Baseline sleep parameters and perceived effectiveness were shown to predict the placebo response of acupuncture for insomnia. Although the study was limited by a small sample size, our findings highlighted the potential implication of sleep duration and sleep-state misperception in the treatment of insomnia.
- Randomized controlled trials
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