Meta-analysis of randomized controlled trials on cognitive effects of Bacopa monnieri extract

Abstract

Ethnopharmacological relevance: Bacopa monnieri has a long history in Ayurvedic medicine for neurological and behavioral defects. To assess its efficacy in improving cognitive function.

Materials and methods: MEDLINE, EMBASE, CINAHL, AMED, Cochrane Central of clinical trial, WHO registry, Thai Medical Index, Index Medicus Siriraj library and www.clinicaltrial.gov were searched from the inception date of each database to June 2013 using scientific and common synonyms of Bacopa monnieri, cognitive performance or memory. The reference lists of retrieved articles were also reviewed. Randomized, placebo controlled human intervention trials on chronic ≥ 12 weeks dosing of standardized extracts of Bacopa monnieri without any co-medication were included in this study. The methodological quality of studies was assessed using Cochrane's risk of bias assessment and Jadad's quality scales. The weighted mean difference and 95% confidence interval (95% CI) were performed using the random-effects model of the Dersimonian-Laird method.

Results: Nine studies met the inclusion criteria using 518 subjects. Overall quality of all included trials was low risk of bias and quality of reported information was high. Meta-analysis of 437 eligible subjects showed improved cognition by shortened Trail B test (-17.9 ms; 95% CI -24.6 to -11.2; p<0.001) and decreased choice reaction time (10.6 ms; 95% CI -12.1 to -9.2; p<0.001).

Conclusion: This meta-analysis suggests that Bacopa monnieri has the potential to improve cognition, particularly speed of attention but only a large well designed 'head-to-head' trial against an existing medication will provide definitive data on its efficacy on healthy or dementia patients using a standardized preparation.

Keywords: ADHD; AVLT; Bacopa monnieri; Brahmi; Cognition; MCI; MMSE; Nootropic; Speed of attention; attention deficit hyperactivity disorder; auditory verbal learning test; mild cognitive impairment; mini mental state examination.