Memory assessment in studies of cognition-enhancing drugs for Alzheimer's disease

There is an increasing number of cognition-enhancing drugs for Alzheimer's Disease (AD) and, consequently, drug trials represent a growing field of in terest in research. As memory dysfunction is generally the first and most s evere cognitive impairment in AD, the choice of memory testing to be used i n these studies is of great importance. It should reflect an understanding of memory systems being assessed with neuropsychological tests and the fact that some tests can be more appropriate than others to show benefit with c ertain classes of cognition-enhancing drugs. Severe deterioration of episodic and semantic memory occurs very early in t he AD process while working memory shows a gradual deterioration over time. Some aspects of working and implicit memory can be spared in the mild to m oderate stages of AD. Tests of working, episodic, semantic and implicit mem ory are used as outcomes in trials with acetylcholinesterase inhibitors, dr ugs with other neurotransmitter strategies, metabolic enhancers and drugs w hich may impact upon a variety of CNS processes. The clinical scales and ob servational measures are largely used in trials of cognition-enhancing drug s for AD (46.66% of all the studies reviewed). The Digit Span test, the Rey Auditory Verbal Learning Test, the Buschke Sel ective Reminding Test and the verbal fluency tasks are the most sensitive m emory tests, whereas the most sensitive scales are the Sandoz Clinical Asse ssment-Geriatric, the Gottfried-Brane-Steel scale and the Blessed Dementia Scale. Finally, we suggest that future investigations should use sensitive memory tests, together with behavioural and psychiatric scales, rather than general observational evaluations.