Response to placebo acupuncture in insomnia: a secondary analysis of three randomized controlled trials.

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.