Attenuation in the Progression of Cognitive Deterioration in Alzheimer's Disease With Rivastigmine: A Dose-Dependent Effect
AbstractObjectives: Possible disease-modifying effects of rivastigmine have been suggested by analyses using a variation of the randomized start design; however, the results were somewhat confounded by differing attrition rates. We report on an alternative method investigating whether increasing doses reduce the rates of cognitive decline in patients who continue treatment.Methods: The effect of dose on the rate of cognitive decline seen on the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) was explored for patients in a long-term (130-week) extension of a 26-week placebo-controlled trial using two methods: a weighted leas squares regression analysis using each individual's slope, and a weighted analysis of variance (ANOVA) comparing the slopes of patients categorized by dose (≤6 mg/d or >6 mg/d).Results: The results from 408 patients included in the weighted least squares analysis estimated the rate of decline to attenuate by approximately 1 point/y for every 3 mg/d increase (P<.0001). The average annual rate of decline for patients whose mean dose was >6 mg/d was 4.5 points (95% Cl, 5.1–3.9), while for patients with a mean dose of≥6 mg/d a decline of 8.2 points (95% Cl, 9.1–7.3) was seen.Conclusion: These data further support earlier results suggesting that rivastigmine reduces the rate of progression of cognitive deterioration in Alzheimer's disease.