Common Causes of Acute Confusion in the Elderly
Infection is the most common precipitating factor for acute confusion (delirium) in elderly patients, particularly urinary tract infections and pneumonia, followed by medications (especially anticholinergics and benzodiazepines), dehydration, and electrolyte disturbances. 1, 2
Most Frequent Infectious Causes
- Urinary tract infections and pneumonia are the most frequently encountered infectious causes of delirium in older adults, accounting for approximately 49% of cases 1, 2, 3
- Over 80% of patients with bacteremia show neurological symptoms ranging from lethargy to coma 1
- Infection should be treated promptly to prevent prolonged delirium, which is associated with worse cognitive and functional recovery 2
Medication-Related Causes
- Anticholinergic medications (including antihistamines like cyclizine) are among the highest-risk medications for causing delirium and should be discontinued 1, 2
- Benzodiazepines are potent precipitants of delirium and should be discontinued unless used to treat alcohol or benzodiazepine withdrawal 1, 2
- Medications account for approximately 30.8% of delirium cases in community-dwelling elderly 3
- Opioids, particularly in patients with renal impairment, can accumulate metabolites and contribute to delirium 1
- The total burden of anticholinergic drugs may determine development of delirium rather than any single agent 4
- Polypharmacy with anticholinergic compounds is common, especially in nursing home residents 4
Metabolic and Electrolyte Disturbances
- Dehydration is a common precipitating factor (26.4% of cases) that may not be apparent on initial laboratory examination 1, 3
- Electrolyte disturbances occur in 18.7% of cases, with hyponatremia being the most common 3
- Hypercalcemia should be suspected even with indolent symptoms such as confusion, asthenia, or somnolence, as delirium due to hypercalcemia is reversible in 40% of cases 1
- Hyponatremia due to SIADH may require specific testing beyond basic metabolic panels 1
Neurological Causes
- Acute mental status changes may be triggered by cerebrovascular disease including traumatic brain injury and stroke 5
- Less frequent neurological causes include status epilepticus, nonconvulsive seizure, intracranial mass effect, chronic subdural or subarachnoid hemorrhage, meningitis or encephalitis, and hydrocephalus 5
- Acute neurological conditions are found in only 18.3% of patients despite 91% having cerebral imaging 3
Multifactorial Etiology Pattern
- Two or more coexisting precipitating causes are frequently encountered in elderly patients with delirium 5
- In the majority of acute confusion cases, the etiology is multifactorial, with infections and dehydration being the most common contributors 6
- Fewer precipitating factors are typically identified at first assessment compared to final assessment (1.4 versus 1.9 factors respectively), indicating that early diagnostic evaluation often misses contributing causes 3
Additional Contributing Factors
- Pain, constipation, and pressure ulcers are often-overlooked factors that should be identified through thorough physical examination 1
- Visual and hearing impairments contribute significantly to delirium; patients should be ensured to use their glasses and hearing aids 1, 2
- Sleep deprivation is both a symptom and a factor that prolongs delirium 1
- Hearing deficits, depression, pulmonary disorders, and abnormal serum sodium or potassium levels are associated risk factors 6
Critical Clinical Context
- Delirium is considered a medical emergency with mortality rates twice as high if the diagnosis is missed 5
- Overall mortality in patients with altered mental status is approximately 8.1% and is significantly higher in elderly patients 5
- 34% of long-term care residents with acute confusion died within 3 months of evaluation 6
- Up to 10-31% of patients may have delirium at admission, and it may develop in up to 56% of admitted patients, particularly following surgery or in the intensive care unit 5