The cardinal features of cognitive and noncognitive dysfunction and the differential efficacy of tacrine in Alzheimer's disease patients.

The Alzheimer's Disease Assessment Scale (ADAS), frequently used in clinical trials to assess overall pathology of Alzheimer's disease (AD), comprises two subscales. The cognitive subscale (ADAS-COG) consists of 11 items, and the noncognitive subscale consists of 9 items. Factor analyses were carried out on ADAS-COG and ADAS-NONCOG item scores from the most recent and largest (n = 663) placebo-controlled, multicenter, 30-week study (970-61) of tacrine in patients with AD conducted by the clinical research group at Parke-Davis Pharmaceutical Research. Through factor analyses the primary dimensions of variation in the ADAS-COG and ADAS-NONCOG were defined. Obliquely rotated three principal factors of ADAS-COG and three principal factors of ADAS-NONCOG have been interpreted as three cardinal features of cognitive function corresponding to memory, language, and praxis, and three cardinal features of noncognitive function corresponding to agitation, depression, and lack of concentration. Reliably defined factors of ADAS-COG enabled comparisons of longitudinal changes in cognitive dysfunction. Factor scores at week 30, adjusted to baseline factor scores, were used to compare the effects of tacrine with those of placebo on cognitive cardinal features. Additionally, the effect of concurrent depression on cardinal features of cognitive dysfunction was evaluated by gender.