Placebo Response Rates in Acupuncture Therapy Trials for Functional Dyspepsia: A Systematic Review and Meta-Analysis

BACKGROUND: Functional dyspepsia (FD) is a functional digestive disease with limited management selection. Previous studies revealed that acupuncture therapy is effective for FD. However, because sham controls were not implemented in most clinical trials following acupuncture therapy, it is difficult to differentiate overall treatment responses from placebo. This study aims to quantify placebo responses in clinical trials in which FD patients received sham manual acupuncture (MA) and sham electroacupuncture (EA). MATERIALS AND METHODS: Randomized controlled trials of MA and EA for FD patients were searched in PubMed, Web of Science, Cochrane Library, and Embase databases, as well as 4 Chinese language databases from inception to January 2021. RevMan 5.20 software was used for pooled analysis of symptom scores and quality of life. The symptom scores were combined using standard mean difference (SMD) or weighted mean difference (WMD) with a 95% confidence interval (CI). The quality of included studies was tested using modified Jadad scale and Standards for Reporting Interventions in Controlled Trials of Acupuncture (STRICTA) checklist. Egger’s test, Begg’s test, and sensitivity analyses were conducted using Stata 11.0 statistical software. The protocol of this study is registered in PROSPERO as CRD42021233858. RESULTS: After screening, the current systematic review included 13 randomized controlled trials, of which 8 studies were used in the meta-analysis. Regarding subjective outcomes, the combined effect of sham MA on FD symptoms was [SMD=−0.42, 95% CI (−0.72, −0.12); P=0.005], whereas sham EA treatment was [SMD=−0.54, 95% CI (−0.81, −0.27); P<0.001]. The combined effect on FD quality of life of post-sham MA group was [SMD=−0.32, 95% CI (−0.52, −0.12); P=0.002]. With regard to objective outcomes, the combined effect of sham EA on dominant frequency was [WMD=−0.11, 95% CI (−0.30, −0.08); P=0.24], while the combined effect of sham EA on dominant power was [WMD=−3.35, 95% CI (−8.04, 1.35); P=0.16]. CONCLUSIONS: Sham MA and sham EA remarkably improve symptoms and quality of life scores of FD without influencing objective outcomes, highlighting the significance of sham controls in acupuncture therapy clinical trials.