Ginkgo biloba extract for dementia: a systematic review

BACKGROUND: Given the increasing burden of dementia internationally and the lack of effective treatments, several countries are already recommending the use of ginkgo biloba extract (GbE) in the treatment of dementia, despite the inconsistent research results about its effectiveness. AIM: Conduct a meta-analysis of studies about the effect of GbE on cognition and daily functioning in persons with dementia. METHODS: Searches of various English and Chinese databases identified reports of placebo controlled, randomized trials of ginkgo biloba treatment (lasting a minimum of 22 weeks) for dementia that were published from January 1982 to September 2012. Data extraction and critical appraisal of studies were conducted using the GRADE system. Heterogeneity, sensitivity and potential publication bias of the studies were evaluated using RevMan 5.1. Pooled results of the metaanalysis were presented as forest plots using standardized mean differences (SMD) in scores for continuous variables and relative risk (RR) for categorical variables. RESULTS: Nine studies with a total of 2578 patients met the inclusion and exclusion criteria. Pooled results from the six studies that were included in the meta-analysis (total n=1917) found that GbE was superior to placebo in preventing deterioration in cognitive functioning and in activities of daily living, but these results were only valid for studies with younger subjects (with a mean age below 75). There were no significant differences in the dropout rates between groups or in the overall rates of adverse events during treatment. However, there was considerable heterogeneity in the results between the studies (primarily based on the age of the subjects) and there were several potential biases in the reports (most of which were supported by pharmaceutical firms), so the overall evidence was considered of ‘low quality’. CONCLUSION: This meta-analysis highlights serious weaknesses in the available studies about this important problem. GbE may be effective in persons under 75 years of age with dementia, but large, placebo controlled, randomized trials focused on milder forms of dementia (including mild cognitive impairment) that compare different doses of GbE and that follow subjects for prolonged periods (at least one year) are needed to confirm this result.