Is traditional Chinese medicine syndrome differentiation important in primary insomnia? An exploratory review with matching recombination indirect comparisons and network meta-analysis

• Syndrome differentiation based acupuncture lacks conclusive superiority for primary insomnia. • Large effect sizes in matched studies show uncertain clinical relevance due to methodological bias. • Syndrome-based acupuncture ranks higher in SUCRA but inconclusive. • Indirect comparisons highlight need for direct trials on syndrome differentiation. Syndrome differentiation is the primary method of Traditional Chinese Medicine (TCM) diagnosis and treatment of diseases and has become the key to the clinical development of acupuncture. However, there is a lack of supporting clinical evidence to determine the impact of syndrome differentiation on the efficacy of acupuncture treatment. Therefore, we aimed to evaluate the importance of point selection based on syndrome differentiation by re-analyzing the trials' results in treating primary insomnia with acupuncture. We systematically searched 9 databases for eligible trials. Two authors extracted data independently from citations, interventions, and outcomes. Since the "treatment acupuncture" and "control acupuncture" data compared in this study were from different trials, we matched the data in a 1:1 ratio and minimized heterogeneity between the paired groups. Matching factors included age, sex ratio, and the baseline Pittsburgh Sleep Quality Index (PSQI) score. Meta-analyses were performed using Revman 5.4 software. STATA 15.0 was used for the network meta-analysis. Effect estimation presented continuous data with a standard mean difference (SMD) with a 95% confidence interval (CI). We included a total of 172 trials. After matching, 19 recombinational pairs of studies were established. Meta-analysis of the 19 pairs showed that PSQI scores in the syndrome differentiation group were lower than the non-syndrome differentiation group (SMD: -0.87, 95%CI -1.46 to -0.28, P =0.004). Network meta-analysis of all included trials showed no statistical difference in acupoints selection between syndrome and non-syndrome differentiation (SMD: -0.40, 95% CI -2.63 to 1.84). However, acupoint selection based on syndrome differentiation (43.9%) ranks higher than acupoint selection based on non-syndrome differentiation (38.0%) according to SUCRA curves. Current evidence does not conclusively support the superiority of syndrome differentiation-based acupuncture over non-syndrome differentiation for primary insomnia. While statistically significant large effect size was observed in matched studies, the clinical relevance of this difference remains uncertain due to methodological limitations, heterogeneity, and inconsistent findings across analytical approaches. Future trials with direct comparisons and standardized outcome measures are needed to clarify the clinical utility of syndrome differentiation in acupuncture therapy.