Cognitive performance in patients with Alzheimer's disease receiving cholinesterase inhibitors for up to 5 years

The cholinesterase inhibitors (ChE-Is) - rivastigmine, donepezil and galantamine - demonstrated efficacy in large, 6-month, double-blind, placebo-controlled trials, and are widely used for the symptomatic treatment of patients with mild-to-moderate Alzheimer's disease (AD). Over the past few years, data have emerged, suggesting that these agents may have long-term benefits. These data have been summarized in this study, followed by an interpretation of clinical relevance. Data were identified by searches of Medline(R) and references from relevant English-language articles. The search words 'Alzheimer', 'donepezil', 'rivastigmine', 'galantamine' and 'long term' were used. In addition, recent data presented at international congresses and/or provided by colleagues in this field of research were included in order to ensure maximum topicality. Data are available showing cognitive performance in patients remaining on rivastigmine for up to 5 years (n = 83), donepezil for up to 4.9 years (n = 18) and galantamine for up to 4 years (n = 185). Most of these data come from open-label studies and need to be interpreted with caution. The data appear to suggest that patients, caregivers and physicians will still see some decline on ChE-Is after a period of stabilization, but this may be slower and later than expected if the patients were left untreated. This applies across all domains of AD - not simply cognition - and function can be relatively preserved, even if cognitive scores are falling. Despite the limitations of current data, the information reviewed in this study may help practising doctors assess the long-term value of ChE-Is in this consistently progressive disease.