Ginkgo biloba is widely used for its potential benefits in improving people's memory and cognition. However, a study of 3,069 people in the U.S. has found that it has no effect in reducing the incidence of dementia or Alzheimer's disease. The participants in the study were all over 75 and 482 of them had mild cognitive impairment. All the participants were evaluated every six months and dementia and Alzheimer's disease were determined by an expert panel. The incidence of dementia and Alzheimer's was actually slightly higher in the gingko biloba group although this was not statistically significant i.e. it was probably due to chance.
DeKosky, S.T. ... [et al] - Ginkgo biloba for prevention of dementia Journal of the American Medical Association 300, 19, 2253-2262