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.
背景: 痴呆的疾病负担不断增加，而且缺乏有效的治疗方法，因此有些国家就推荐使用银杏叶提取物（ginkgo biloba extract, GbE）来治疗痴呆，虽然有关 GbE 疗效的研究结果尚不一致。
目的: 就银杏叶提取物对痴呆患者认知功能和日常生活能力改善作用的研究进行meta分析。
方法: 检索国内外数据库，找出 1982 年 1 月— 2012 年 9 月发表的关于银杏叶提取物治疗（不少于 22 周）痴呆患者的随机安慰剂对照研究的文献报告。根据 GRADE 系统推荐的方法进行文献质量评估并提取资料。采用 RevMan 5.1 软件进行异质性检验、敏感性分析并评估发表偏倚。对连续性变量的合并效应值采用标准均差（Standardized mean differences, SMD）表示，对分类变量则采用相对危险度（relative risk, RR）表示， meta 分析的合并结果采用森林图显示。
结果: 有 9 项研究共计 2578 例患者符合入组和排除标准。其中 6 项研究共计 1917 例患者纳入 meta 分析，结果发现仅在样本年龄相对较低（平均年龄 75 岁以下）的研究中 GbE 在延缓认知功能衰退和防止日常活动能力下降方面优于安慰剂。组间脱落率以及治疗中总的不良事件发生率均无显著差异。然而，不同研究结果间存在明显的异质性（主要是因为研究对象的年龄差异），文献存在可能的发表性偏倚（大多数是医药公司资助的），因此总体证据强度属于“低”。
结论: 这一 meta 分析表明，现有对此重要问题的研究证据依然极其薄弱。GbE 对 75 岁以下存在痴呆的人群可能有效。需要大样本、安慰剂对照的随机研究来验证上述结果，今后的研究应当聚焦于程度较轻的痴呆（包括轻度认知功能障碍），比较不同剂量 GbE 的效果，并且随访更长的时间（至少 1 年）。