There were 65 studies in the review. Thirty-two trials included participants with normal cognition, 22 included participants with mild cognitive impairment, and 11 included both types of participant. The overall quality of the trials was judged to be moderate; most trials had limitations in methodology or analysis.
Three trials (89 participants) investigated donepezil or memantine. One trial found an improvement only in sematic recall when using donepezil. The other trials found no evidence of a benefit.
Oestrogen was used in seven trials (10,792 women). Three of these trials found a relative decline in cognitive function and an increase in dementia with oestrogen (hazard ratio 1.8, 95% confidence interval: 1.2 to 2.6). Testosterone was used in three trials (144 men), with conflicting results. Dehydroepiandrosterone hormonal therapy was used in three trials (317 participants), with no evidence of any effect.
Gingko was used in two trials (348 participants), with no evidence of any effect.
Vitamins and fatty acids (6,779 participants) also were found not to have any effect.
Three trials (244 participants, table 1) investigated physical exercise. Results were inconclusive, with statistically significant benefits for some aspects of cognitive function, but not for others.
Cognitive training was used in three trials (3,321 participants), with some evidence that it may be beneficial.