What are the key differences in diagnosis and management of delirium vs dementia?

Delirium vs Dementia: Key Diagnostic and Management Differences

Delirium is a medical emergency requiring urgent intervention, characterized by acute onset (hours to days) and fluctuating course, while dementia develops insidiously over months to years with progressive decline—distinguishing between them is critical because missing delirium can be fatal. 1

Critical Diagnostic Distinctions

Temporal Profile (Most Important Differentiator)

• Delirium: Acute onset developing over hours to days with minute-to-hour fluctuations in mental status 1, 2
• Dementia: Insidious onset over months to years with gradual, progressive decline 2

Core Clinical Features

Delirium presents with: 1, 2

• Inattention (cardinal feature—inability to focus, sustain, or shift attention)
• Altered level of consciousness (ranging from hyperalert to stuporous)
• Acute fluctuations (symptoms vary dramatically within the same day)
• Disorganized thinking (rambling, incoherent speech, illogical flow)
• Sleep-wake cycle disruption, perceptual disturbances (hallucinations), delusions, and emotional lability

Dementia presents with: 1

• Memory impairment (particularly delayed recall) as primary feature
• Preserved consciousness and attention (until advanced stages)
• Stable symptoms throughout the day without acute fluctuations
• Progressive functional decline in activities of daily living

Subtypes of Delirium (Commonly Missed)

• Hyperactive: Agitation, hypervigilance, hallucinations 2
• Hypoactive: Psychomotor slowing, sedated appearance—most frequently missed 2
• Mixed: Alternating between hyperactive and hypoactive states 1

Diagnostic Approach

For Suspected Delirium (Urgent Evaluation Required)

Step 1: Establish baseline cognitive function 1

• Interview knowledgeable informant immediately to determine patient's previous cognitive, functional, and behavioral baseline
• Document exact timeline of symptom onset and progression

Step 2: Apply validated screening tool 1, 2

• Confusion Assessment Method (CAM) is gold standard with 82-100% sensitivity and 89-99% specificity 2
• CAM requires: (1) acute onset AND fluctuating course, (2) inattention, AND either (3) altered consciousness OR (4) disorganized thinking 2
• Perform repeated assessments throughout the day to capture fluctuations 1

Step 3: Rapid bedside attention testing 2

• Recite months of year backward (MOTYB)
• Short Orientation Memory Concentration Test (SOMCT)

Step 4: Simultaneously identify underlying causes 1, 2

• Comprehensive medication review (especially anticholinergics, benzodiazepines, opioids)
• Cognitive lab panel (CBC, electrolytes, glucose, renal/hepatic function, thyroid, B12)
• Search for infection (urinalysis, chest X-ray, blood cultures)
• Assess for hypoxia, dehydration, organ failure
• Review for drug intoxication or withdrawal

For Suspected Dementia (Non-Urgent Evaluation)

Step 1: Validated cognitive screening 1

• Brief tools (5-10 minutes): Mini-Cog, MoCA-4 item version, GP Assessment of Cognition (GPCOG)
• Comprehensive tools (15-30 minutes): Montreal Cognitive Assessment (MoCA)—more sensitive for mild cognitive impairment than MMSE 1

Step 2: Functional assessment 1

• Evaluate instrumental activities of daily living (medication management, finances, transportation)
• Assess basic activities of daily living in moderate-to-severe cases

Step 3: Informant interview 1

• Obtain collateral history about gradual cognitive decline over months to years
• Document impact on daily functioning

Critical Management Differences

Delirium Management (Medical Emergency)

Immediate priorities: 1, 2

• Treat underlying cause(s) urgently—infection, metabolic derangement, medication toxicity, hypoxia, organ failure
• Non-pharmacological interventions first: reorientation, sleep hygiene, early mobilization, sensory aids (glasses, hearing aids), family presence
• Pharmacological management only when patient poses danger to self/others or when non-pharmacological measures fail
• Prevent complications: falls, pressure ulcers, aspiration, dehydration

Prognosis if untreated: Fatal or devastating irreversible cognitive and functional losses 1, 2

Dementia Management (Chronic Disease)

Long-term approach: 1

• Comprehensive diagnostic workup to determine etiology (Alzheimer's, vascular, Lewy body, frontotemporal)
• Neuropsychological testing when office-based assessment insufficient 1
• Specialist referral for atypical presentations or early-onset (age <65) 1
• Disease-modifying therapies when appropriate
• Symptomatic management and caregiver support

Critical Pitfall: Delirium Superimposed on Dementia

This combination has devastating consequences: 1

• Accelerated cognitive and functional decline
• Increased length of hospital stay
• Higher rates of rehospitalization, institutionalization, and death
• Greater healthcare costs compared to dementia alone

Key management principle: 3

• Wait 2-4 weeks after complete delirium resolution before performing formal cognitive testing for dementia
• Premature testing during or immediately after delirium yields unreliable results and may lead to misdiagnosis 3

Urgency Classification

Delirium: Urgent/emergent evaluation and management required 1, 2

• Mortality doubles if diagnosis missed 1
• Economic impact: $38-152 billion annually in the United States 1

Rapidly progressive dementia (weeks to months): Urgent evaluation, often requiring inpatient workup 1

Typical dementia (months to years): Non-urgent but expedited evaluation, usually outpatient 1