Long-term cognitive benefits of donepezil in Alzheimer's disease: A retrospective comparison between 1994-1999 and 2000-2004

Objective: In order to address an issue of how long Alzheimer's disease (AD) patients should receive donepezil, we estimated long-term effect of donepezil on cognition as well as its influential factors. We also evaluated the additional effect of cerebrospinal fluid (CSF)-tau protein levels on diagnosis. Methods: We compared cognitive changes between current (2000-2004) AD patients (donepezil users) and previous AD patients, seen by us 1994-1999, without receiving donepezil (non-donepezil users) by a mixed effect model. Cognition was assessed by Mini-Mental State Examination (MMSE) at 6-month intervals up to 24 months. Sensitivity analysis was performed exclusively on patients with high CSF-tau protein levels (CSF-tau >330 pg/mL) to minimize inaccuracies of the diagnosis . Results: From 495 AD patients reviewed, 192 patients (120 donepezil users and 72 controls) were eligible, Estimated annual decline of MMSE was 1.2 points (95% confidence interval (95%CI), 0.9-1.5) in the donepezil users, whereas it was 2.8 points (95%CI, 2.1-3.6) in the control group. The difference was statistically significant (P < 0.001). The sensitivity analysis demonstrated that these declines were 1.2 (95%CI, 0.8-1.6) and 3.1 (95%CI, 2.3-3.9) points in the donepezil users and control groups, respectively. Conclusions: Long-term donepezil use for at least 2 years appeared to be beneficial in maintaining cognition in AD patients. As the cholinergic central nervous system consistently degenerates over time, long-term use of donepezil may be an appropriate therapy. Discontinuation of donepezil may not be recommended as far as patients are in a stable condition.