Analysis of outcomes of randomized controlled trial on compound Chinese herbal medicine formulas in treatment of vascular cognitive impairment caused by cerebral small vessel

The purpose of the study is to analyze the outcomes of randomized controlled trial(RCT) of Chinese herbal medicine formula(CHMF) in the treatment of vascular cognitive impairment caused by cerebral small vessel disease(CSVD-VCI), and provide suggestions for future studies in this field. Three English databases, four Chinese databases, and two online registration websites of clinical trials were searched with use of the search strategy established in advance. Relevant RCTs published in recent ten years were screened, and necessary information was extracted to assess the risk of bias and analyze the outcomes of these RCTs. As a result, a total of 10 461 articles were retrieved, of which 8 681 were kept after de-duplication, and 41 RCTs were included after screening, with a generally higher risk of bias. The outcomes of included RCTs were classified into 9 categories, namely, clinical symptom outcomes, neuroimaging outcomes, neuroelectrophysiological outcomes, blood biochemical outcomes, hemorheology outcomes, physical signs, syndrome scores of traditional Chinese medicine(TCM), clinical effective rate, and safety outcomes. Among them, the most frequently reported outcomes of included RCTs were blood biochemical outcomes, and clinical symptom outcomes showed the highest reporting rate. Besides, 9 RCTs reported syndrome scores of TCM as the outcomes and illustrated corresponding evaluation criteria. The analysis showed that the application of RCT outcomes in this field had clinical rationality and limitations, and there were also some deficiencies in the trial design level, namely, no distinction between primary and secondary outcomes, insufficient blind methods, not detailed description of outcomes, disunity of evaluation tools, and despised endpoint outcomes. These limitations and deficiencies were negatively affecting the quality of RCTs of CHMF in the treatment of CSVD-VCI. Therefore, we suggest that future researchers should be well prepared in the top-level design stage, and actively construct the core outcome set of this field, so as to improve the quality of clinical trials.