Chinese Herbal Medicine for Mild Cognitive Impairment Using Montreal Cognitive Assessment: A Systematic Review.

BACKGROUND: Mild cognitive impairment (MCI) prevalence is estimated at 6%-12% of the population. It is possible that early treatment at the MCI stage could reduce progression to more severe cognitive impairment. The Montreal Cognitive Assessment (MoCA) is a sensitive measure used to assess changes in cognitive function. Various Chinese herbal medicines (CHMs) have been tested for effects on MCI using MoCA.

OBJECTIVES: To evaluate the clinical evidence for CHMs on MoCA scores in MCI.

DESIGN: Five biomedical databases in English and Chinese language were searched for randomized controlled trials that compared orally administered CHMs with a control group and assessed changes in cognition using MoCA. Analyses were based on the comparison, control intervention, and study duration. Mean differences and 95% confidence intervals were calculated to evaluate treatment effects. For each study, risk of bias was assessed according to the Cochrane tool.

RESULTS: Nineteen studies were included with 16 contributing to the data analyses. Three studies were placebo controlled. Nine compared a CHM with a pharmacotherapy, three combined a CHM with a pharmacotherapy, and one combined CHM with cognitive training. In the two placebo-controlled studies of 24-week duration, results favored the CHMs at end of treatment.

CONCLUSIONS: The systematic review suggests that the oral application of certain CHMs improved scores on MoCA by 1.76-2.34 points compared with placebo in people with MCI after 24 weeks of treatment. However, these two studies used different CHM formulations. Two studies that tested the same CHM formulation, Bu Yang Huan Wu Tang, in combination with donepezil, reported improvement in the integrative groups, but the studies were not blind and the durations were only 8-12 weeks. Overall, methodological weaknesses limited the strength of the evidence. The herbal formulae included ingredients that have received considerable research attention for their effects on memory and cognition. PROSPERO international prospective register of systematic reviews protocol registration number: CRD42018099650.