Is single acupoint Sanyinjiao (SP 6) effective in managing insomnia? A systematic review of randomized controlled trials.

Insomnia is a symptom of physical or mental disorder and refers to decreased sleep time and potentially low quality. There is evidence showing that acupuncture could enhance management of insomnia, and Sanyinjiao (SP 6) is one of the promising acupoints. This review aimed to evaluate the effectiveness of stimulating single acupoint SP 6 in managing insomnia. The study was registered under PROSPERO CRD42019140855. English and Chinese databases were searched for randomized controlled trials on single acupoint SP 6 stimulation in management of insomnia. Quality of methodology was assessed by two authors independently using the Cochrane Risk of Bias Tool, and reporting quality was assessed by the STRICTA checklist. The primary outcome was the Pittsburgh Sleep Quality Index (PSQI), and secondary outcomes were improvement in clinical effect and sleep duration assessed by polysomnogram (PSG). The extracted data were pooled and meta-analyzed with RevMan 5.3 software. Four trials involving 288 participants were included in this review. The findings showed that SP 6 stimulation could improve sleep quality (MD -0.30, 95% CI [-0.52, -0.08]), lengthen deep sleep duration (MD 80.46, 95% CI [56.47, 104.45]), rapid eye movement (REM) duration (MD 91.53, 95% CI [68.41, 114.65]), and increase improvement in clinical effect. Quality of reporting and methodology was limited in all included trials. Some limited evidence showed that single acupoint stimulation of SP 6 could improve sleep quality, lengthen deep sleep and REM duration of patients with insomnia. However, the findings in this review should be interpreted with caution due to methodological limitations.