Efficacy of herbal medicine treatment based on syndrome differentiation for Parkinson's disease: A systematic review and meta-analysis of randomized placebo-controlled clinical trials

Background: Parkinson's disease (PD), the second most common progressive neurodegenerative disease, causes heterogeneous clinical symptoms. Patients experience a range of motor and non-motor symptoms, and personalized diagnosis and treatment are needed. In traditional East Asian medicine, syndrome differentiation (SD) is a diagnostic approach for customized therapy that uses a comprehensive analysis and varies for the same disease. We aimed to evaluate the efficacy of herbal medicine (HM) prescribed according to the SD of PD.Methods: Ten electronic databases were searched from inception to August 2021 without language limitations. All randomized controlled trials (RCTs) involving HM for SD of PD were included. Assessment of Cochrane's risk of bias and meta-analysis and Grading of Recommendations Assessment, Development, and Evaluation was also performed. Effect measurement was summarized using the mean difference (MD) with 95% confidence interval, through a meta-analysis.Results: Thirteen RCTs involving 843 participants were included. The overall risk of bias was either low or unclear. Compared with the placebo, a combined therapy of HM and Western medicine (WM) significantly improved the total Unified Parkinson's Disease Rating Scale (UPDRS) (MD = -8.03, [-10.27, -5.79], p < 0.00001; I-2 = 0%) and was more beneficial, as assessed using the UPDRS (I-III), the Parkinson's Disease Questionnaire-39, and the Non-Motor Symptoms Scale. Adverse events did not differ between the groups.Conclusion: The findings suggest that the combined treatment of WM and HM based on SD diagnosis has additional benefits in PD treatment. However, the methodological quality of the included RCTs was suboptimal. Nevertheless, this systematic review is the first to investigate the efficacy of HM treatment according to the SD diagnosis in PD. The clinically meaningful improvement in HM according to SD in PD needs to be tested in further studies with rigorous designs and longer follow-up periods.Systematic Review Registration: [], identifier [INPLASY2021100020].