Can delirium be separated from dementia?

This presentation reviews the nosological status of delirium and dementia as a prelude to a discussion of how to distinguish them, or even if they are distinguishable. It argues that committee (ICD, DSM) classification systems fossilise the meaning of the syndromes, and thereafter have a baleful effect on research. The distinction between dementia and delirium is a case in point, and it can be argued that this is much less clear than we thought. It is suggested that validation of syndromes as prognostic tools is a logical way out of the nosological swamp into which delirium and dementia research is sinking, and that cognitive improvement should be the key distinction.