银杏叶提取物无助于预防痴呆 请勿随意服用
在以身心健康的老人为对象的双盲检试验中发现，银杏叶提取物的改善认知功能效果实际上仅仅与安慰剂相当。即使健康的人为了“防止痴呆”而服用银杏叶提取物，似乎也没有多大的意义。该研究结果刊登在《Journal of American Medical Association（JAMA）》2002年8月21日号上。
银杏叶提取物是在德国作为药品、在日本和美国作为健康食品销售的药物成份。在以血管性痴呆及老年痴呆病人为对象的安慰剂对照试验中发现，如果每天服用并至少持续4星期的话，就可以略微延缓痴呆症的发生。
但是，在以认知功能属于正常范围的人为对象的试验中尚未发现具有防止（延缓）痴呆“发病”的效果。尽管如此，在美国却一直进行着有助于防止健康老人痴呆发病的错误宣传，于是有不少人因此而服用银杏叶提取物。
为此，美国Williams大学心理系的Paul R. Solomon通过刊登新闻广告征集“身心健康且无痴呆症的60岁以上的男性及女性志愿者”。将前来应征的98名男性和132名女性老人随意分成两组，并请他们服用了6个星期的安慰剂或银杏叶提取物（40mg，每天3次）。
自愿参与试验者的平均年龄为69岁，其中40%为男性。智力检查的一种――精神状态简易速检表检查（MMSE检查、30满分，26分以上属于正常范围）的平均分数为28.8分。研究小组在志愿人员服用前后进行了WAIS-R试验及WMS-R试验等测试记忆力及注意力等认知功能的试验，并就14个项目比较了服用前后的得分情况。
结果发现，服用银杏叶提取物和服用安慰剂的志愿者在几乎所有项目上的得分均出现了上升。一上升幅度无论是从统计学还是从临床学来看，均未出现实际药物和安慰剂之间的明显差别。在朋友及家人的客观评价中，两组间也未出现差别。
研究小参照此次试验结果，批评了对先期进行的痴呆安慰剂对照试验结果的解释。并指出，尽管依据非常不充分，但是在德国每年却开出500万张的处方单、在美国1997年的销售额则高达240万美元。该研究小组提醒人们不要随意服用这种药物。
该论文的题目是“Ginkgo for Memory Enhancement”。 以下为原文内容：Ginkgo for Memory Enhancement A Randomized Controlled Trial
JAMA.2002;288:835-840.Context Several over-the-counter treatments are marketed as having the ability to improve memory, attention, and related cognitive functions in as little as 4 weeks. These claims, however, are generally not supported by well-controlled clinical studies. Objective To evaluate whether ginkgo, an over-the-counter agent marketed as enhancing memory, improves memory in elderly adults as measured by objective neuropsychological tests and subjective ratings. Design Six-week randomized, double-blind, placebo-controlled, parallel-group trial. Setting and Participants Community-dwelling volunteer men (n = 98) and women (n = 132) older than 60 years with Mini-Mental State Examination scores greater than 26 and in generally good health were recruited by a US academic center via newspaper advertisements and enrolled over a 26-month period from July 1996 to September 1998. Intervention Participants were randomly assigned to receive ginkgo, 40 mg 3 times per day (n = 115), or matching placebo (n = 115). Main Outcome Measures Standardized neuropsychological tests of verbal and nonverbal learning and memory, attention and concentration, naming and expressive language, participant self-report on a memory questionnaire, and caregiver clinical global impression of change as completed by a companion. Results Two hundred three participants (88%) completed the protocol. Analysis of the modified intent-to-treat population (all 219 participants returning for evaluation) indicated that there were no significant differences between treatment groups on any outcome measure. Analysis of the fully evaluable population (the 203 who complied with treatment and returned for evaluation) also indicated no significant differences for any outcome measure. Conclusions The results of this 6-week study indicate that ginkgo did not facilitate performance on standard neuropsychological tests of learning, memory, attention, and concentration or naming and verbal fluency in elderly adults without cognitive impairment. The ginkgo group also did not differ from the control group in terms of self-reported memory function or global rating by spouses, friends, and relatives. These data suggest that when taken following the manufacturer's instructions, ginkgo provides no measurable benefit in memory or related cognitive function to adults with healthy cognitive function.
Author Affiliations: Department of Psychology (Dr Solomon and Ms Zimmer), Program in Neuroscience (Dr Solomon and Mss Adams, Silver, and Zimmer), Department of Mathematics and Statistics (Dr DeVeaux), Williams College, Williamstown, Mass; and The Memory Clinic, Southwestern Vermont Medical center, Bennington (Dr Solomon).