Blood-Letting Therapy for Hypertension: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Objective: To evaluate the efficacy and safety of blood-letting therapy (BLT) in treatment of hypertension. Methods: A comprehensive electronic and manual bibliographic searches were performed in Cochrane Central Register of Controlled Trials, Excerpt Medica Database (EMBASE), PubMed, China National Knowledge Infrastructure, Chinese Scientific Journal Database, Chinese Biomedical Literature Database, and Wanfang Database to identify randomized controlled trials (RCTs) in which hypertensive patients were treated with BLT or BLT plus antihypertensive drugs (BPAD) against placebo, no treatment or antihypertensive drugs. The Cochrane Risk Assessment Tool was used to assess the methodological quality of trials. The Review Manager 5.3 software was used for meta-analysis. Results: A total of 7 RCTs with 637 hypertensive patients from 1989 to 2017 were identified. Compared with antihypertensive drugs, blood pressure was significantly reduced by BLT (RR=1.21, 95% CI: 1.01 to 1.44, P=0.03; heterogeneity: P=0.06, I2=60%) and BPAD (RR=1.25, 95% CI, 1.02 to 1.53, P=0.03; heterogeneity: P= 0.01, I2=71%). Moreover, a significant improvement in Chinese medicine syndrome by BLT (RR=1.32; 95% CI: 1.14 to 1.53, P=0.0002; heterogeneity: P=0.53, I2=0%) and BPAD (RR=1.47; 95% CI: 1.06 to 2.04, P=0.02; heterogeneity: P=0.13, I2=56%) was identified. The reported adverse effects were well tolerated. Conclusions: Although some positive findings were identified, no definite conclusions regarding the efficacy and safety of BLT as complementary and alternative approach for treatment of hypertension could be drew due to the generally poor methodological design, significant heterogeneity, and insufficient clinical data. Further rigorously designed trials are warranted to confirm the results.