The Alzheimer’s Disease Assessment Scale–Cognitive Subscale (ADAS-Cog; Rosen et al, 1984) is a performance-based instrument that measures the specific cognitive dysfunctions associated with Alzheimer’s disease. It is considered to be a more sensitive instrument of cognitive function than the Mini-Mental State Examination. The ADAS-Cog is the most common scale used in cholinesterase inhibitor trials, and meets FDA requirements for objective performance-based scales used to measure efficacy in clinical trials.

The ADAS-Cog is an 11-item cognitive subscale that objectively measures memory, language, orientation, and praxis. With a total score range of 0 to 70, a patient with mild to moderate Alzheimer’s disease has an average ADAS-Cog total score of 15 to 25 points.

A longitudinal study of Alzheimer’s disease (Stern et al, 1994) demonstrated that the estimated decline in ADAS-Cog scores was approximately 9 to 11 points per year in patients with untreated mild to severe Alzheimer’s disease residing in the community (n = 111) and mean and median baseline ADAS-Cog scores of 35.1 and 33, respectively. Although different studies have shown different rates of cognitive decline, one study reported an annual decline of 7 to 8 points in patients with Alzheimer’s disease (Kramer-Ginsberg et al, 1988).