The response-time relationship and covariate effects of acupuncture for chronic pain: a systematic review and model-based longitudinal meta-analysis.

Background and Objective Critical clinical questions regarding how soon and how long the analgesic effect will be achieved by acupuncture, as well as who will be responsive to acupuncture, need further address. The aim of the study was to investigate the response-time relationship and covariate effects of acupuncture. Databases and Data Treatment PubMed and EMBASE were searched up to December 2018 for randomized controlled trials that involved sham acupuncture, true acupuncture and conventional therapy. We used a model-based longitudinal meta-analysis to characterize the response-time profile of these treatments. Results Seventy-seven randomized clinical trials involved chronic shoulder, neck, knee and low back pain were included. The response-time analysis suggested that the treatment duration of acupuncture will be 5 weeks or more to achieve 80% of maximum analgesic effect. Moreover a lower baseline pain intensity and the location of low back pain resulted in a lower pain relief of acupuncture intervention. The absolute maximum analgesic effects of sham acupuncture and conventional therapy were 22.6 and 15.8 points at a 0-100 NRS scale. The absolute effect of true acupuncture was 26.1 points for low back pain (relative effect of 3.5 and 9.4 points to sham and conventional therapy), 34.9 points for other pain body locations (relative effect of 12.3 and 19.1 points to sham and conventional therapy), in patients with a baseline pain intensity of 60 points. Conclusion The treatment duration of acupuncture will not be less than 5 weeks to achieve 80% maximum analgesic effect. Higher analgesic effect was related to higher baseline pain intensity and pain location of neck, shoulder and knee. Significance Our systematic review and meta-analysis provides the clear evidence for the treatment duration and significant related covariates of acupuncture intervention for chronic pain. These results provide useful suggestion for acupuncture intervention in clinical pain management.