Why Delirium Occurs

Delirium occurs as a result of a complex interplay between patient vulnerability to delirium and precipitating factors (See Table). Patients who are highly vulnerable (e.g., 97 year old nursing home patient with severe dementia and is bedridden) require a relatively benign precipitating factor (e.g., simple urinary tract infection) to develop delirium. Patients who have little vulnerability to delirium (e.g., a fully functional 66 year old without dementia who still balances his/her own checkbook) require a more noxious precipitating factor (e.g., severe sepsis) to develop delirium. Because older patients are more likely to have multiple vulnerability factors, they are more susceptible to becoming delirious compared with their younger counterparts. When a patient with little or no vulnerability factors presents with delirium, one should have increased concern for an underlying life threatening illness.

Vulnerability Factors	Precipitating Factors
Advanced age Dementia Low education attainment Functional impairment Immobility Multimorbidity Sensory impairment Polypharmacy Substance abuse history Dehydration Malnutrition Depression	Infection Metabolic disturbances Electrolyte disturbances Organ failure CNS insults Medication toxicity Endocrine dysfunction Recreational drug use Ethanol or benzodiazepine withdrawal Trauma / Pain Hypo- or hyperthermia
Table.Vulnerability and precipitating factors for delirium. CNS, central nervous system.

Why Delirium Occurs

Read more about why delirium occurs

Altered mental status in older patients in the emergency department.

Delirium in elderly people.