Clinical Implication of Delirium Subtype

Delirium is a common and serious condition which is often under-detected and under-treated. This may be partly due to a lack of concensus regarding the definition of its subtypes. Subtypes of delirium may be explained according to different pathophysiologic mechanisms. Three subtypes (hyperactive, hypoactive, mixed) of delirium, based on arousal disturbance and psychomotor behavior have been identified. However, definitions may vary from author to author. Irrespective of the way delirium is diagnosed and the subtypes defined, the hypoactive subtype is more prevalent than the hyperactive. Despite this prevalence, a diagnosis of hypoactive delirium is often missed, and rather ismost frequently misdiagnosed as depression or dementia. The hypoactive delirium subtype may be less responsive to antipsychotic drug therapy than the hyperactive delirium subtype. Clinical subtypes of delirium may provide information concerning the etiology, the pathogenesis, and the prognosis of delirium, but also may have therapeutic consequences. There remains no consensus regarding the optimal classification system for delirium subtypes. More studies are needed to isolate two, three, or more delirium subtypes, in terms of predicting factors, outcome predictors, and therapeutic management.