Background There are debates in acupuncture related systematic reviews and meta-analyses on whether searching Chinese databases to get more Chinese-language studies may increase the risk of bias and overestimate the effect size, and whether the treatment effects of acupuncture differ between Chinese and non-Chinese populations.Methods In this meta-epidemiological study, we searched the Cochrane library from its inception until December 2021, and identified systematic reviews and meta-analyses with acupuncture as one of the interventions. Paired reviewers independently screened the reviews and extracted the information. We repeated the meta-analysis of the selected outcomes to separately pool the results of Chinese- and non-Chinese-language acupuncture studies and presented the pooled estimates as odds ratios (OR) with 95% confidence interval (CI). We calculated the Ratio of ORs (ROR) by dividing the OR of the Chinese-language trials by the OR of the non-Chinese-language trials, and the ROR by dividing the OR of trials addressing Chinese population by the OR of trials addressing non-Chinese population. We explored whether the impact of a high risk of bias on the effect size differed between studies published in Chinese- and in non-Chinese-language, and whether the treatment effects of acupuncture differed between Chinese and non-Chinese population.Results We identified 84 Cochrane acupuncture reviews involving 33 Cochrane groups, of which 31 reviews (37%) searched Chinese databases. Searching versus not searching Chinese databases significantly increased the contribution of Chinese-language literature both to the total number of included trials (54% vs. 15%) and the sample size (40% vs. 15%). When compared with non-Chinese-language trials, Chinese-language trials were associated with a larger effect size (pooled ROR 0.51, 95% CI 0.29 to 0.91). We also observed a higher risk of bias in Chinese-language trials in blinding of participants and personnel (97% vs. 51%) and blinding of outcome assessment (93% vs. 47%). The higher risk of bias was associated with a larger effect estimate in both Chinese-language (allocation concealment: high/unclear risk vs. low risk, ROR 0.43, 95% CI 0.21 to 0.87) and non-Chinese-language studies (blinding of participants and personnel: high/unclear risk vs. low risk, ROR 0.41, 95% CI 0.23 to 0.74). However, we found no evidence that the higher risk of bias would increase the effect size of acupuncture in Chinese-language studies more often than in non-Chinese-language studies (the confidence intervals of all ROR in the high-risk group included 1, Table 3). We further found acupuncture appeared to be more effective in Chinese than in non-Chinese population (Table 4).Conclusions The findings of this study suggest the higher risk of bias may lead to an overestimation of the treatment effects of acupuncture but would not increase the treatment effects in Chinese-language studies more often than in other language studies. The difference in treatment effects of acupuncture was probably associated with differences in population characteristics.

Background Acupuncture is widely used worldwide, and systematic reviews on acupuncture are increasingly being published. Although acupuncture systematic reviews share several essential elements with other systematic reviews, some essential information for the application of acupuncture is not covered by the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement. Considering this, we aimed to develop an extension of the PRISMA statement for acupuncture systematic reviews. Methods We used the PRISMA statement as a starting point, and conducted this study referring to the development strategy recommended by the EQUATOR network. The initial items were collected through a wide survey among evidence users and a review of relevant studies. We conducted a three-round Delphi survey and one-day face-to-face meeting to select items and formulate the checklist. After the consensus meeting, we drafted the manuscript (including the checklist) and sent it to our advisory experts for comments, following which the checklist was refined and circulated to a group of acupuncture systematic review authors for pilot test. We also selected a sample of acupuncture systematic reviews published in 2017 to test the checklist. Results A checklist of five new sub-items (including sub items) and six modified items was formulated, involving content related to title, rationale, eligibility criteria, literature search, data extraction, and study characteristics. We clarified the rationales of the items and provided examples for each item for additional guidance. Conclusion The PRISMA for Acupuncture checklist is developed for improving the reporting of systematic reviews of acupuncture interventions.