Relationship of disease severity to decline on specific cognitive and functional measures in Alzheimer disease

Previous studies have shown that the sensitivity of global cognitive and functional measures to change in Alzheimer disease is related to overall disease severity. The present study assessed the sensitivity to decline, over a 12-month interval, for individual items of the cognitive portion of the Alzheimer Disease Assessment Scale (ADAS-Cog), the Instrumental Activities of Daily Living Scale (IADLS), and the Physical Self-Maintenance Scale (PSMS). This study was conducted in an effort to identify individual items likely to be sensitive at different stages of the disease. A total of 151 patients with Alzheimer disease were classified into four dementia categories by baseline scores on the Blessed Test of Information, Memory, and Concentration. The patients were retested after 12 months. For the individual items and for total scores on both the ADAS-Cog and the IADLS, rate of change was greater for patients in the moderate and severe categories than for mild or very severe patients. For individual items and for the total score on the PSMS, rate of change was greater for severe and very severe patients than for patients with mild or moderate disease.