What is confusion, and what can cause it?

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Doctors use the term “delirium” to refer to the changes in mental state that most people associate with confusion.

Also, doctors use “delirium” to describe the sudden onset of confusion. This requires immediate medical attention.

Some symptoms of delirium include:

• having trouble focusing or paying attention
• feeling disconnected from time or place — a person might believe that they are living in the past, for example
• forgetting basic facts, such as the year or who the president is
• having an altered state of consciousness, which may make them seem very sleepy or agitated
• not recognizing familiar faces
• experiencing changes in movement, such as problems with reflexes, developing tics, or wandering aimlessly
• having changes in language or the ability to express oneself

The causes of confusion, or delirium, can be complex, and they tend to relate to another health issue.

For instance, a person with dementia might develop confusion after surgery, after a fall, or after starting to take certain medication.

When a person has a condition that increases the risk of confusion, such as dementia, there is usually a specific trigger.

Below are some common causes of confusion.

Age

Age is a significant risk factor for confusion. Various studies estimate that 10–25% of older people who are hospitalized have symptoms of confusion when they arrive at the hospital.

Age is also the most significant risk factor for dementia, as well as for mild cognitive impairment.

Mild cognitive impairment is associated with age-related memory and thinking problems. These are more severe than those that occur with regular aging, and in some people, mild cognitive impairment precedes dementia.

Medications

Any drug that changes a person’s mental state may cause confusion, especially in people with other risk factors for this issue.

Some examples include:

• antihistamines
• sleeping medications
• benzodiazepines, a group of antianxiety drugs
• opioids, such as oxycodone
• anesthetics

Also, some people develop confusion after taking antibiotics, antidepressants, or any of a wide range of medications.

Surgery

Many people develop confusion after surgery, particularly as the anesthetic is just beginning to wear off.

This tends to be more common among older people — about 15–25% of older people may experience confusion after minor surgeries, while as many as half experience confusion after major surgeries, such as a hip replacement.

Also, pain, pain medication, and unfamiliar surroundings after surgery can contribute to confusion.

Chronic illness

Numerous chronic illnesses can cause confusion, especially when they progress to damage organs, including the brain.

Some examples include:

• diabetes
• AIDS
• cancer
• organ failure, such as from kidney or liver disease

Sensory issues

People with sensory problems, such as trouble hearing or seeing, may be more prone to confusion, particularly in new settings. This, too, is more common among older people.

A person who does not have access to their usual assistive devices is even more vulnerable to confusion, such as when an older person leaves their hearing aids at home before going to the hospital.

Unfamiliar surroundings

Some people develop confusion in unfamiliar settings, particularly during periods of intense stress.

People with other risk factors for confusion, such as dementia, are more likely to experience this issue in unfamiliar places, without the memory cues and references points that they usually rely on.

Brain health issues

Any health problem that affects the brain can cause confusion.

Dementia is one of the most common causes of delirium, or confusion, in older people, but delirium does not mean that a person has dementia.

Any injury or illness that changes brain function may cause delirium. Some examples include:

• head injuries that cause concussion
• infections in or around the brain
• swelling of the brain
• lesions, growths, or cancer in the brain

Other causes

Virtually any health condition can trigger confusion, especially in people with risk factors.

Some other potential causes of confusion include:

• stress and anxiety
• intense pain
• sleep deprivation
• malnourishment
• changes in the endocrine system, which produces hormones

Older people have a higher risk of developing delirium — a sudden onset of confusion. Anyone who experiences this should receive urgent medical care.

Research suggests that older adults with delirium and other health issues have a less favorable outlook, overall. For example, a person hospitalized for breathing issues may have a higher risk of returning to the hospital or dying if they also have delirium.

A person can have delirium as well as dementia, and dementia increases the risk of delirium. It can sometimes be difficult to distinguish between the two issues.

In hospitals, about half of older people who have dementia also have delirium.

For some older people, confusion during an illness is an early warning sign of dementia. For others, an illness worsens preexisting dementia symptoms.

Some older people develop new or worsening confusion when they are sick, especially if they have dementia.

Also, urinary tract infections often cause confusion in older people.

A headache and confusion can signal a serious health problem, such as a stroke or brain injury.

Seek immediate care for these symptoms, especially if the headache feels different from headaches in the past.

However, not all headaches that cause confusion are emergencies — some people with migraine headaches develop confusion during episodes.

Anyone who gets headaches frequently should consult a doctor about how to tell when to seek emergency help or schedule an appointment.

Confusion is sometimes a fleeting problem with a clear cause. Children may be confused when they wake up in the middle of the night, and exhausted adults may be confused after a nap, for example.

However, when the cause is unclear, it is important to receive medical attention right away, as the issue can stem from a wide range of serious medical conditions.

Receive emergency medical care if:

• There is chest pain or signs of a stroke, such as changes in vision or slurred speech.
• There are signs of an infection, such as a fever.
• The person becomes disconnected from reality, hallucinates, or loses consciousness.
• A child develops confusion without any apparent cause.
• Confusion develops after starting a new medication.

Confusion that develops without a clear cause can result from a serious health problem. But many issues that cause confusion are highly treatable — the person may simply need antibiotics, fluids, or monitoring in a hospital.

Overall, the earlier a person receives care, the better their outlook is.

For people with other health problems, their prognosis tends to be more serious if they also develop confusion. This includes people with chronic illnesses and those who have just had surgery.

Receiving medical care right away can help ensure that a person with confusion receives the right diagnosis, and it can significantly improve their outlook.

Someone with confusion may find it difficult to answer a healthcare provider’s questions. It can help for a knowledgeable loved one to accompany them.

Be prepared to answer questions about when the confusion began and other elements of the person’s medical history.