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The objective was to identify separate cognitive domains in the standard assessment tools (MMSE, ADAS-Cog) and analyze the process of decline within domains during three years in Alzheimer's disease (AD) patients with donepezil treatment.

Fortunately, basic research is identifying many of the pathways that contribute to this devastating disease (Fig. 1), providing unprecedented opportunities for the development of new treatments aimed at the root causes of AD. Here, we review several of these efforts and consider both shorter- and longer-term prospects for effectively treating AD.

Molecular and cellular processes presumed to participate in AD pathogenesis. Aß peptides produced by neurons and other brain cells aggregate into a variety of assemblies, some of which impair synapses and neuronal dendrites, either directly or through the engagement of glial loops. Build-up of pathogenic Aß assemblies could result from increased production or aggregation or from deficient clearance mechanisms. ApoE4 and tau promote Aß-induced neuronal injury and also have independent adverse effects. Microglia could be beneficial or harmful, depending on which of their signaling cascades and functions are engaged. This multifactorial scenario leads to progressive disintegration of neural circuits, isolation and loss of neurons, network failure, and neurological decline.

Five drugs are approved in the United States for the treatment of AD (2, 3), although tacrine is now rarely used because of hepatotoxicity (Table 1). Cholinesterase inhibitors are designed to combat impairment of cholinergic neurons by slowing degradation of acetylcholine after its release at synapses. Memantine prevents overstimulation of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors, which may contribute to the pathogenesis of AD and other neurodegenerative conditions by causing excitotoxicity (4). In clinical trials, both cholinesterase inhibitors and memantine have shown beneficial but modest effects on cognitive test scores, behavioral measures, and functional outcomes (5–9). However, because the benefits of cholinesterase inhibitors are small and may be seen in only a subset of patients, their cost effectiveness has been questioned (10). Because memantine is beneficial in patients already taking cholinesterase inhibitors and may even reduce their side effects, the two are often used together (9). Many AD patients also receive antipsychotics or anti-depressants to manage neuropsychiatric and behavioral symptoms or take over-the-counter preparations whose therapeutic value is uncertain, including ginkgo biloba and vitamins C and E

The effectiveness of the 5 U.S. Food and Drug Administration–approved pharmacologic therapies for dementias in achieving clinically relevant improvements is unclear.

Purpose: To review the evidence for the effectiveness of cholinesterase inhibitors (donepezil, galantamine, rivastigmine, and tacrine) and the neuropeptide-modifying agent memantine in achieving clinically relevant improvements, primarily in cognition, global function, behavior, and quality of life, for patients with dementia.

Data Synthesis: 96 publications representing 59 unique studies were eligible for this review. Both cholinesterase inhibitors and memantine had consistent effects in the domains of cognition and global assessment, but summary estimates showed small effect sizes.