Dementia: continuum or distinct entity?

The latent structure of dementia was examined in a group of 10,775 older adults with indicators derived from a neuropsychological test battery. The author conducted taxometric analysis of these data using mean above minus below a cut, maximum covariance, and latent mode factor analysis and found results more consistent with dementia as a dimensional (lying along a continuum) than categorical (representing a distinct entity) construct. A second study conducted with a group of 2,375 adults whose ages ranged from 21 to 64 years produced similar results. These findings denote that dementia, as measured by deficits in episodic memory, attention and concentration, executive function, and language, differs quantitatively rather than qualitatively from the cognitive status of adults without dementia. The implications of these results for classification, assessment, etiology, and prevention are discussed.