Delirium in elderly patients is a sudden and severe change in brain function that leads to confusion, disorientation, and altered consciousness. It is not a disease itself but rather a symptom or syndrome caused by various underlying factors. The main causes of delirium in older adults are diverse and often interrelated, reflecting the complexity of aging bodies and brains.
One of the most common causes of delirium in elderly patients is **infections**, especially urinary tract infections (UTIs). UTIs are particularly frequent triggers because older adults often have weakened immune systems, making infections more likely to spread before obvious symptoms appear. The body’s immune response to infection causes inflammation, which can temporarily disrupt brain function and lead to confusion. Pneumonia and meningitis are other infections that can similarly provoke delirium. Infections may not always present with typical signs like fever or pain in older adults; instead, sudden confusion or behavioral changes may be the first indication of illness.
**Metabolic disturbances** are another major cause. These include electrolyte imbalances such as low sodium or potassium levels, dehydration, and abnormalities in blood sugar or kidney and liver function. Such imbalances affect the brain’s chemical environment, impairing its ability to function properly. Dehydration is especially common in the elderly due to reduced thirst sensation and other health issues, and it can exacerbate delirium by causing low blood volume and poor circulation to the brain.
**Medications and drug effects** play a significant role in delirium among the elderly. Older adults often take multiple medications (polypharmacy), increasing the risk of drug interactions and side effects. Certain drugs are notorious for causing delirium, including anticholinergics, benzodiazepines, opioids, antidepressants, antipsychotics, and some antihistamines. These medications can alter neurotransmitter levels or cause toxic effects on the brain. Additionally, withdrawal from alcohol or sedatives can precipitate delirium.
**Central nervous system (CNS) disorders** such as strokes, brain tumors, traumatic brain injuries, and neurodegenerative diseases like Parkinson’s or dementia can cause delirium by directly damaging brain tissue or disrupting normal brain signaling. Cognitive decline itself makes the brain more vulnerable to delirium when other stressors occur.
**Cardiorespiratory problems** contribute by reducing oxygen supply to the brain. Conditions like anemia, heart failure, pulmonary embolism, or chronic obstructive pulmonary disease (COPD) can cause hypoxia (low oxygen) or hypercapnia (high carbon dioxide), both of which impair brain function. Acute cardiovascular events such as heart attacks or strokes also increase delirium risk.
Other important factors include **major surgery and trauma**, which can trigger delirium through pain, anesthesia effects, blood loss, and the stress response. Postoperative delirium is common in elderly patients, especially after hip fractures or cardiac surgery.
**Sleep deprivation and sensory impairments** such as hearing or vision loss can also contribute. Poor sleep disrupts brain chemistry and cognitive function, while sensory loss can cause the brain to misinterpret or fill in missing information, sometimes leading to hallucinations or confusion.
Additional causes include **constipation, urinary retention, nutritional deficiencies (like vitamin B12 or thiamine), endocrine disorders (such as thyroid problems or diabetes), and exposure to toxins or heavy metals** like lead or mercury.
In essence, delirium in elderly patients results from a complex interplay of infections, metabolic imbalances, medication effects, brain disorders, oxygen deprivation, physical trauma, and sensory or sleep disturbances. The aging brain’s reduced resilience means that even relatively minor insults can tip the balance toward delirium. Identifying and addressing these underlying causes promptly is crucial to managing delirium and improving outcomes in older adults.