Longitudinal evaluation of dementia of the Alzheimer type

We administered 3 commonly employed tests of mental status (the Information-Memory-Concentration test [IMC], the Mini-Mental State Examination [MMSE], and the Dementia Rating Scale [DRS]) to 92 patients with probable dementia of the Alzheimer type. The 3 tests were readministered to 55 of the patients (2-year subgroup) approximately 1 year later, and administered a 3rd time to 20 of the patients (3-year subgroup) approximately 2 years after their initial assessment. In all cases, scores on the 3 tests were highly correlated with each other. Examination of the annual rate of change (ARC) in score for the 2-year subgroup revealed an average decline of -3.24 error points on the IMC, 2.81 points on the MMSE, and 11.38 points on the DRS. Of the 3 tests, only the DRS evidenced greater sensitivity to change with increasing dementia severity. In the 3-year subgroup, the ARC between years 1 and 2 was not correlated with ARC between years 2 and 3 for any of the 3 tests. This finding suggests that a patient's rate of progression in 1 year may bear little relationship to future rate of decline.