The Impact of Drugs against Dementia on Cognition in Aging and Mild Cognitive Impairment

Objective: To define the actual knowledge of the impact of drugs for the treatment of dementia on the improvement of cognition in aging and mild cognitive impairment. Method: We conducted a Medline search for studies with the parameters drug and cognition. Only drugs that had demonstrated cognition improvements in dementia according to actual methodological standards were included. Drugs had to be approved in at least one American or European nation. Results: Donepezil, galantamine, Ginkgo biloba EGb 761® (definition see editorial), memantine and rivastigmine fulfilled these criteria. There were no systematic investigations on the effects of these drugs on cognition in healthy adults or patients with mild cognitive impairment (MCI). Regarding Ginkgo biloba, two studies on MCI patients could be identified. In healthy adults, we could only include one study investigating donepezil and seven investigating Ginkgo biloba EGb 761®. According to the findings, donepezil significantly increased the percentage of REM sleep and REM density, whereas REM latency was reduced. This was interpreted as a sign of improved cognition. Ginkgo biloba EGb 761® improved cognition in healthy controls according to Delayed Free Recall and Delayed Recognition of the WAIS-III and the Color Naming of the Stroop Test as well as in MCI in Digit Copying, Dual Coding Task and speed of response on a computerized version of a classification task. The highest effects were observed after 6 weeks of treatment with 180 mg/d. Conclusions: Due to the lack of standard procedures for investigating cognition improvement in healthy aging, results have to be interpreted cautiously. In healthy adults as well as in individuals categorized as having MCI, Ginkgo biloba EGb 761® improved cognition in some but not all neuropsychological tests. The single positive result with donepezil raises hope that other drugs may also contribute to cognitive improvement, even in healthy adults. However, the data do not allow any conclusions regarding an improvement following a specific ”neuropsychological cluster.” Studies on prevention have not been completed so far.

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1 A heterogeneous group of individuals was investigated in 37 retirement homes. Only 39 or 40 individuals (different numbers were reported) were classified as suffering from dementia. However, no imaging was performed. This means that in the mean, one individual with dementia was investigated by an undefined ”rater” in each retirement home. These results will show an extraordinary variance, making every outcome random. In fact, no efficacy of the drug could be demonstrated in a huge amount of statistical tests.