BACKGROUND: Alzheimer's disease (AD) is the most common cause of dementia in later life. It is manifested by gradual and progressive decline in cognitive function and ability to perform activities of daily living (ADL) and the development of behavioral disturbances. Progressive reduction in functional ability reduces independence and quality of life and adversely affects caregivers and society. Therefore, benefit from any AD therapy may be obtained not only from improved function but also from stabilization or reduced worsening of function. METHOD: This retrospective study of pooled data from 3 randomized, placebo-controlled trials (N = 2126) compared the incidence of different levels of worsening between 2 rivastigmine treatment groups and a placebo group at week 26 for cognition, using the Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog); global functioning, using the Clinicians' Interview-Based Impression of Change-Plus (CIBIC-Plus); and ADL, using the Progressive Deterioration Scale (PDS). Categories of worsening analyzed for each scale were as follows: ADAS-Cog: any decline, >/= 4-point decline, >/= 7-point decline; CIBIC-Plus: stabilized/worsened (rating = 4, 5, 6, or 7), any worsening (rating = 5, 6, or 7); PDS: any worsening, >/= 10% worsening. RESULTS: Patients treated with rivastigmine, 6-12 mg/day, showed significantly less decline in cognition, global functioning, and ADL for all categories of worsening examined compared with patients who received placebo. The reduction in decline compared with placebo was greater in the group receiving 6-12 mg/day of rivastigmine compared with the treatment group receiving 1-4 mg/day of rivastigmine. CONCLUSION: Rivastigmine reduces the amount of worsening observed in cognition, global functioning, and ADL in a 6-month trial period.