Confusion: Causes and What to Do

What confusion looks like

A confused person may:

• not know where they are, the date or time
• have trouble following a conversation or switching topics oddly
• be unusually sleepy or, the opposite, agitated and restless
• see or hear things that are not there
• forget recent events or repeat questions
• behave out of character, or be fine at one moment and muddled the next

Fluctuation, especially worse in the evening (sundowning), is typical of delirium.

Sudden confusion vs gradual confusion

People with dementia are much more likely to develop delirium, so a sudden worsening in someone with dementia needs medical assessment rather than being put down to their illness.

Causes of sudden confusion

Infections

Urinary tract infections, pneumonia and skin infections commonly cause confusion in older adults, sometimes without fever. Sepsis, meningitis and encephalitis cause confusion at any age.

Metabolic problems

• Low blood sugar: sweating, shaking and confusion in people on insulin or some diabetes tablets. It responds to sugar within minutes.
• High blood sugar: in very uncontrolled diabetes.
• Low sodium: from some diuretics, antidepressants, drinking excess water, or illness.
• Dehydration, high calcium, and kidney or liver failure (hepatic encephalopathy).
• Low oxygen or high carbon dioxide from lung disease, heart failure or sleep apnea.

Brain causes

• Stroke and transient ischemic attack.
• Head injury, including a slow bleed (subdural hematoma) in older adults on blood thinners, which can appear days or weeks after a minor fall.
• Seizures and the period afterward.
• Brain infections and tumors.

Medicines, alcohol and drugs

Common culprits are sleeping pills, benzodiazepines, opioids, anticholinergic drugs (some bladder pills, older antihistamines), steroids and multiple medicines together. Alcohol intoxication or withdrawal, and recreational drugs, also cause confusion.

Other triggers

Surgery and anesthesia, constipation, urinary retention, pain, sleep deprivation, a change of surroundings and poor eyesight or hearing all add up, especially in older people.

Causes of gradual confusion

• Alzheimer's disease, vascular dementia and Lewy body dementia
• Underactive thyroid
• Vitamin B12 deficiency
• Depression, which can mimic dementia
• Normal pressure hydrocephalus (with walking problems and urinary incontinence)
• Long-term alcohol misuse

How doctors find the cause

Doctors check alertness and attention with short tests (for example naming the months backward), look for focal neurological signs and infection, and review all medicines. Tests usually include a finger-prick blood sugar, oxygen level, blood count, sodium, calcium, kidney and liver function, urine tests and a chest X-ray. A CT or MRI brain scan is done for head injury, stroke signs, or no clear cause. A lumbar puncture checks for meningitis or encephalitis.

How to help someone who is confused

• Stay calm, speak simply, and introduce yourself.
• Remind them gently where they are and what day it is.
• Make sure they have their glasses and hearing aids.
• Keep the room well lit during the day and quiet at night.
• Offer fluids, and make sure they can reach the toilet.
• If they have diabetes and are awake and able to swallow, check blood sugar or give a sugary drink if it is low.
• Do not leave a newly confused person alone, and get medical help.

Treatment targets the cause: antibiotics, fluids, correcting blood sugar or sodium, stopping problem medicines. Delirium can take days to weeks to clear fully, even after the cause is treated.

Frequently asked questions

What causes sudden confusion in elderly people?

The most common causes are infections such as urinary or chest infections, dehydration, new or changed medicines, constipation, urinary retention, low sodium and stroke. Older people may not have a fever. Sudden confusion is delirium and needs same-day medical assessment.

Is confusion a sign of stroke?

It can be, especially with sudden face drooping, arm weakness, trouble speaking, vision loss or severe dizziness. Call 911 or your local emergency number immediately. Stroke treatment works best within the first few hours.

Can a UTI cause confusion?

Yes, especially in older adults, who may become confused, agitated or sleepy with few urinary symptoms. However, confusion should not be blamed on a urine infection without looking for other causes, as positive urine tests are common in older people without infection.

What is the difference between delirium and dementia?

Delirium starts suddenly, fluctuates and affects attention and alertness. It is usually caused by an acute illness and can often be reversed. Dementia develops slowly over months to years and steadily affects memory and thinking.

How long does confusion from delirium last?

Most delirium improves within days once the cause is treated, but in older or frail people it can last weeks. Some people have lasting problems with thinking afterward. Early recognition and treatment improve recovery.