Delirium versus major neurocognitive disorder: one of these is an emergency
Two stacked timeline tracks sharing a broken axis: an upper jagged line oscillating across 72 hours with evening peaks, a lower smooth line descending gently across five years, joined by a dashed vertical rule marked NEW CHANGE TODAY.
DELIRIUM crit | MAJOR NEUROCOGNITIVE DISORDER (dementia) | |
|---|---|---|
| Onset | Hours to days | Months to years |
| Course over 24 hours | Fluctuates; worse in the evening and at night | Stable across the day; slowly progressive over months |
| Attention | Impaired, and this is the hallmark; the patient cannot sustain or shift focus | Preserved until late in the illness |
| Level of consciousness | Altered; ranges from hypoactive and quiet to hyperactive and agitated | Clear until late |
| Reversibility | Reversible when the cause is treated | Not reversible; treatable contributors are ruled out first |
| Most common causes | Infection including urinary tract infection and pneumonia, hypoxia, medications and anticholinergic burden, electrolyte derangement, substance withdrawal, uncontrolled pain, urinary retention, constipation | Alzheimer disease, vascular, Lewy body, frontotemporal |
| First nursing action | Assess for a physiological cause and report it: oxygen saturation, vital signs, glucose, hydration, and a full medication review | Maintain routine, orient with simple one-step cues, secure the environment, support the caregiver |
Reading the two columns
Hypoactive delirium is the one that is missed. A quiet older adult who has become withdrawn and inattentive is not settling in; she is inattentive because something physiological is wrong. Attention is the discriminator you can test in thirty seconds. Ask the patient to say the months of the year backward from December, or to count backward from twenty. A patient with an established neurocognitive disorder may fail the content but will track you; a delirious patient loses the thread of the task itself.
The overlap
Sundowning occurs in both, so evening agitation alone does not decide it. Delirium is more likely, not less, in a patient who already has a neurocognitive disorder. New confusion in a patient with dementia is delirium until proven otherwise.
Memory hook: FAST and FLUCTUATING is delirium. SLOW and STEADY is the disorder.
Watch outsudden confusion is a vital sign. Treating it as a behavior problem, or medicating it with an antipsychotic before a cause is sought, is the classic wrong action. Tick box: can I name three reversible causes?
→ BOOK 10 · P9 for the medical derangements themselves. → BOOK 07 · P6 for every value.
Takeawayacute change in attention means look for a medical cause now, not a psychiatric explanation later.