The relationship between cognitive functioning and disease severity with depression in dementia of the Alzheimer's type

Abstract

This study was conducted to determine the relationship between cognitive and functional impairment in depressed and non-depressed patients with Alzheimer's disease (AD). Subjects (N = 1,486) met NINCDS-ADRDA criteria for possible or probable AD; 183 where diagnosed with a DSM-III-R depressive disorder. All subjects resided in the community. The Mini-Mental States Examination (MMSE) assessed cognitive functioning and the Blessed-Roth Dementia Rating Scale (BRDRS) assessed functional abilities. A depression score was calculated based on the number of endorsed DSM-III-R major depression symptoms. Regression analyses determined the contribution of cognitive (MMSE) and functional severity (BRDRS) in explaining the depression score, while controlling for the effects of: demographic/psychosocial variables, history of depression, and current diagnosis of depression. Cognitive and functional impairment were found to be significantly related to depression. Also, as cognitive impairment and functional abilities worsened, the number of reported depressive symptoms increased. The results of this study underscore the importance of being aware of emotional factors which may compromise cognitive/functional skills in individuals with AD. In addition, depression can be present in all stages of the illness.