Episodic memory and visuospatial ability in detecting and staging dementia in a community-based sample of very old adults.

Abstract

This study examined the efficacy of a cognitive test battery in detecting and staging dementia in a community-based sample of very old adults. The sample consisted of 398 nondemented and 108 demented adults taken from all the inhabitants in the Kungsholmen parish of Stockholm, Sweden (2,368 individuals), aged 75 years and older, who were part of a large-scale epidemiological study on aging and dementia. Participants received a cognitive test battery that consisted of specialized episodic memory tasks, as well as standardized psychometric measures of visuospatial ability and primary memory. A discriminant analysis revealed that highly supported episodic memory tasks (recognition, cued recall) were primarily responsible for correctly classifying normal old adults (94.5%) from those with the diagnosis of dementia (66.7%). Using the Mini-Mental State Exam (MMSE) as the criterion of dementia severity, a correct classification of 88.9% was achieved for mildly demented subjects and 77.8% for moderately demented subjects. Visuospatial tasks made the greatest contribution in distinguishing those at different levels of dementia severity. The results of this investigation indicate that cognitively supported measures assessing episodic memory may be particularly useful in the detection of dementia, whereas visuospatial measures are more effective in staging the disease. Consistent with biological models of the progression of dementia, this suggests that visuospatial abilities may deteriorate later and/or at a slower rate than episodic memory skills in the early stages of dementia. It is noteworthy that these conclusions are based on samples of very old adults taken from the general population.