2022 Feb 22. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–.
Altered mental status is one of the most common presenting symptoms in elderly patients often related to 3 Ds- delirium, dementia, and depression. Out of the 3 Ds, Delirium and dementia are more commonly encountered in clinical practice. Most of the time, the two terms are used interchangeably and therefore unrecognized on the initial assessment. It is critically important to understand that delirium and dementia are distinct syndromes with different prognoses and management. While an acute confusional state that fluctuates and develops over days to weeks is likely to be delirium, a more persistent and chronic progression suggests dementia. This distinction is blurred in cases of persistent delirium and reversible dementia. Cognition is assessed in six domains: memory and learning, language, executive functioning, complex attention, perceptual-motor, and social cognition.
Delirium is characterized by altered awareness mainly affecting attention, whereas dementia is defined as cognitive decline, which interferes with 1 or more domains. Delirium is an abrupt onset of reduced orientation or awareness to the environment in contrast to dementia which is a gradual process leading to disturbance in the core features, and attention is affected much later in the disease course.
Typically, dementia is a neurodegenerative disorder seen in older age and is of various subtypes with the age of onset depending on the subtype. On the other hand, delirium is an age-independent process that occurs more commonly in elderly patients and can happen under variable circumstances. Delirium typically occurs from hours to days, versus dementia is a slow progressive course over months to years. Often the two coexists in the elderly, and sometimes when the dementia is rapidly progressive. It can be difficult to differentiate the two in patients without a prior history of dementia. Therefore, it becomes essential to distinguish between the two or to discern if superadded delirium in a pre-existing dementia patient (delirium superimposed dementia or DSD) leads to a prolonged hospital stay and accelerated cognitive and functional decline, increased healthcare costs, and ultimately death.