What are the potential differentials for an older adult presenting with confusion at night?

Differentials for Confusion at Night in Older Adults

Delirium is the most critical differential for nighttime confusion in older adults and must be assumed until proven otherwise, as missing this diagnosis doubles mortality risk. 1, 2

Primary Differential: Delirium (Medical Emergency)

Delirium should be the working diagnosis for any older adult presenting with acute confusion at night because it:

• Characteristically fluctuates over the course of the day with lucid intervals, often worsening at night (sundowning) 1
• Includes inattention as a cardinal feature with subtle disturbances in consciousness 1
• Occurs in 10-31% of patients at admission and develops in up to 56% of admitted patients 1
• Has mortality rates twice as high when missed 1, 2

Most Common Precipitating Causes of Delirium:

• Infections (most common): urinary tract infections and pneumonia 1, 3
• Medications: anticholinergics, benzodiazepines, narcotics, psychoactive drugs 1, 4
• Metabolic/endocrine disorders: thyroid dysfunction, electrolyte abnormalities, hypoglycemia/hyperglycemia 1, 5, 6
• Intoxication or withdrawal from alcohol or substances 1
• System or organ dysfunction: cardiac, hepatic, renal failure 1
• Two or more coexisting causes frequently occur together 1

Secondary Differentials (After Excluding Delirium)

Dementia with Behavioral Disturbances

• Dementia with Lewy Bodies (DLB): recurrent visual hallucinations occur in up to 80% and form a core diagnostic criterion 2
• Alzheimer's disease: major irreversible cause with sleep-wake cycle disruptions common 1, 6
• Vascular dementia/vascular cognitive impairment 1
• Dementia patients are more vulnerable to superimposed delirium 1

Sleep Disorders Causing Nocturnal Confusion

• Sleep deprivation/insomnia: chronic sleep disruption predicts postoperative delirium and cognitive impairment 1, 7
• Obstructive sleep apnea: contributes to cognitive symptoms and confusion 1, 7
• Circadian rhythm disorders: common in older adults and neurodegenerative diseases 1
• Restless legs syndrome: disrupts sleep quality 7

Neurological Causes (Less Frequent)

• Status epilepticus or nonconvulsive seizures 1
• Stroke or transient ischemic attack 1
• Chronic subdural hematoma or subarachnoid hemorrhage 1
• Meningitis or encephalitis 1
• Intracranial mass effect or elevated intracranial pressure 1
• Normal-pressure hydrocephalus: potentially reversible cause 6

Psychiatric Disorders (Consciousness Intact)

• New-onset psychosis: delusions and hallucinations with preserved awareness and consciousness 1, 2
• Depression with psychotic features: can present with hallucinations 2
• Bipolar disorder: hallucinations during manic or mixed episodes 2
• Psychiatric disorders account for up to 46% of cases when medical causes are excluded 2

Medication-Induced Cognitive Impairment

• Anticholinergic burden: polypharmacy with anticholinergic compounds determines delirium risk 4
• Benzodiazepines: especially long-acting agents cause or exacerbate confusion 7, 4
• Cardiovascular medications: digoxin, beta-blockers, diuretics 1, 4
• Psychotropic medications: SSRIs, SNRIs, antipsychotics 1, 8, 9
• H2 receptor antagonists, corticosteroids, NSAIDs, antibiotics: all can cause idiosyncratic confusion 4

Metabolic and Endocrine Causes

• Thyroid dysfunction: hyperthyroidism causes insomnia and irritability; hypothyroidism causes depression and cognitive changes 5, 6
• Vitamin deficiencies: potentially reversible cause of dementia 6
• Electrolyte disturbances, hypoglycemia, hyperglycemia 1

Critical Diagnostic Algorithm

Step 1: Assess Level of Consciousness

• Impaired or fluctuating consciousness → Delirium until proven otherwise 2
• Intact consciousness → Consider primary psychiatric disorder or neurodegenerative disease 2

Step 2: Characterize Hallucinations (if present)

• Visual hallucinations → Strongly favor medical cause (delirium, DLB, medication toxicity) 2
• Auditory hallucinations → Consider primary psychosis or delirium 2
• Olfactory hallucinations → Immediately investigate for neurological pathology 2

Step 3: Temporal Pattern

• Acute onset (minutes to days) with fluctuation → Delirium 1
• Chronic progressive decline → Dementia 1, 6
• Worsening at night (sundowning) → Delirium or dementia with behavioral disturbances 1

Step 4: Use Validated Assessment Tools

• Confusion Assessment Method (CAM) or variants (CAM-ICU, B-CAM) for delirium screening 1
• Richmond Agitation Sedation Scale or Glasgow Coma Scale to quantify severity 1

Critical Pitfalls to Avoid

• Never attribute new-onset confusion to "just dementia" or "just depression" without excluding delirium and medical causes, as this can miss life-threatening conditions 2, 6
• Do not start antipsychotics before ruling out delirium and medical causes, as this masks the underlying process and increases mortality risk in dementia-related psychosis 8, 9
• Always review the complete medication list including over-the-counter preparations, as polypharmacy and anticholinergic burden are major contributors 1, 7, 4
• Remember that multiple etiologies commonly coexist in older adults with confusion 1
• Thyroid function testing should be performed early as thyroid disorders are common, reversible causes of both cognitive and behavioral symptoms 5, 6