Placebo Response Among Different Types of Sham Acupuncture: A Meta-Analysis of Randomized Controlled Trials for Low Back Pain

Background: Various types of sham acupuncture are used in acupuncture clinical trials, and the placebo response of sham acupuncture have substantial impact on the study outcomes. However, the magnitude of the placebo response and whether it differs across different types of sham acupuncture is unclear. Hence, we conducted a meta analysis to investigate the magnitude of the placebo response of sham acupuncture and whether different types of sham acupuncture have different responses in the studies of acupuncture for nonspecific low back pain (LBP). Methods: PubMed, Embase, MEDLINE, and the Cochrane Library was searched, and randomized clinical trials (RCTs) were included if they randomized patients to receive acupuncture or sham acupuncture treatment. The outcomes included the change in pain intensity, back-specific function and quality of life etc. Random-effects models was used to synthesize the results, standardized mean differences (SMDs, Hedges’ g) were applied to estimate the effect size. Findings: In total, 17 RCTs were included in this meta-analysis, sham acupuncture showed a noteworthy pooled placebo response (SMD −1 · 50, 95% CI −2·03 to −0·96, I 2 = 88%) in pain intensity. A significant placebo response was also shown in back-specific functional status, but not in quality of life. Trials in which the sham acupuncture penetrated the skin, performed with regular needles had a significantly higher placebo response, but other variables such as the location of sham acupuncture did not have a significantly impact on the placebo response. Interpretation: Sham acupuncture is associated with large placebo response in pain intensity, and researchers should be aware that the types of sham acupuncture applied may influence the results of trials. Trial Registration Details: The study protocol was registered at https://www.crd.york.ac.uk/prospero/display_record.php? RecordID=304416. Funding Information: The National Natural Science Foundation of China (82174234). Declaration of Interests: The authors have no conflicts of interest to declare.