Placebo effect was influenced by publication year in three-armed acupuncture trials.
OBJECTIVE
We investigated the relationship between the placebo effect and the trial or patient characteristics.


METHODS
We identified randomized clinical trials with acupuncture, sham and no-treatment groups in which no-treatment or conventional therapy was applied to the no-treatment group. Thirty-one trials in which no treatment was applied in the no-treatment group were categorised as 'strict' trials. Thirty-nine trials in which no-treatment or conventional therapy was applied to the no-treatment group were categorised as 'less strict' trials. We calculated the treatment effect, defined as the difference in the effect size between the acupuncture and no-treatment groups, and the placebo effect, defined as the difference in the effect size between the sham and no-treatment groups. Then, a random effect meta-regression analysis was performed on the two effects with respect to trial or patient characteristics.


RESULTS
The treatment effect was not found to be associated with any factors in both the strict and less strict trials. However, the placebo effect was found to be associated with the publication year in both the strict and less strict trials (P=0.009 and 0.005, respectively). The placebo effect increased by 0.05 in effect size per year in trials that were published more recently.


CONCLUSIONS
While the treatment effect was not influenced by any trial or patient characteristics, the placebo effect was associated with the publication year.
Honam Research Center, Medifarm Hospital, Suncheon, Republic of Korea.
Seo Ryang
SR
We
Yun Hyung
YH
Koog
Min Sun
MS
Park
Byung-Il
BI
Min
D015670:Acupuncture Therapy; D006801:Humans; D017063:Outcome Assessment, Health Care; D010506:Periodicals as Topic; D015990:Placebo Effect; D010919:Placebos; D011643:Publishing / Q000639:trends; D016032:Randomized Controlled Trials as Topic; D012044:Regression Analysis
D010919:Placebos