Sudden confusion is not normal aging. Confusion that starts over hours or days can be delirium, caused by an infection, a medicine or another acute illness. Confusion that comes with face drooping, arm or leg weakness, slurred speech, loss of vision or balance, or a sudden severe headache can be a stroke. Call your local emergency number straight away.
Key points
- Occasional forgetfulness, such as misplacing keys or taking longer to recall a name, is common with age. Dementia is not a normal part of aging.
- In dementia, problems with memory, thinking, language, judgment or behaviour are bad enough to interfere with daily life. Alzheimer disease is the most common cause, contributing to about 60 to 70% of cases worldwide (WHO).
- Early warning signs include repeating the same questions, getting lost in familiar places, trouble handling money or following a recipe, and losing track of the date or season.
- Several treatable problems can cause or worsen memory loss: depression, thyroid disease, low vitamin B12, medicine side effects, alcohol, sleep problems, and kidney or liver disease.
- A rapid change in thinking over hours or days needs same-day or emergency assessment. It is more likely to be delirium or a stroke than Alzheimer disease.
What is Alzheimer disease?
Alzheimer disease is a brain disease that slowly damages memory and thinking. Brain changes such as amyloid plaques and tau tangles begin a decade or more before symptoms appear, a stage called preclinical Alzheimer disease. Not everyone with these brain changes goes on to develop dementia (NIA).
The WHO estimates that 57 million people were living with dementia worldwide in 2021, with nearly 10 million new cases each year, and over 60% of them live in low- and middle-income countries. Age is the strongest known risk factor. For most people with Alzheimer disease, symptoms start in their mid-60s or later. Young-onset dementia, which begins before age 65, accounts for up to 9% of cases (WHO).
Other types of dementia include vascular dementia, dementia with Lewy bodies and frontotemporal dementia, and mixed forms often occur together.
Normal aging or a warning sign?
With age, many people learn new things more slowly and occasionally forget a word, an appointment or where they put something. The key difference is the effect on daily life. The NIA compares them like this:
| Usually normal aging | Possible sign of dementia |
|---|---|
| Making a bad decision once in a while | Making poor judgments and decisions much of the time |
| Missing a monthly payment | Problems taking care of monthly bills |
| Forgetting which day it is and remembering later | Losing track of the date or time of year |
| Sometimes forgetting which word to use | Trouble having a conversation |
| Losing things from time to time | Misplacing things often and being unable to find them |
Early warning signs
Memory problems are usually one of the first signs of Alzheimer disease, but changes in other thinking skills can come first. Signs that should prompt a visit to a doctor include:
- forgetting recently learned information and asking the same questions again and again
- getting lost in places you used to know well, or while walking or driving
- trouble planning, solving problems or following a recipe or directions
- trouble handling money and paying bills
- losing track of dates, the time of year or where you are
- difficulty finding the right word or following a conversation
- misjudging distances or having trouble understanding what you see
- putting things in odd places and being unable to retrace steps to find them
- taking much longer to finish everyday tasks
- changes in mood, personality or behaviour, including new anxiety, irritability, apathy or withdrawal from work and social activities
The WHO notes that changes in mood and behaviour sometimes appear before memory problems. Family members often notice the changes before the person does.
Mild cognitive impairment (MCI) means more memory or thinking problems than other people of the same age, while the person can still look after themselves and carry out everyday tasks. MCI can be an early sign of Alzheimer disease, but not everyone with MCI develops it (NIA).
Treatable causes to check first
Memory problems can come from conditions unrelated to dementia, and these often improve once treated. The NIA lists:
- depression, anxiety and major stress or grief
- thyroid, kidney or liver problems
- low levels of important nutrients, such as vitamin B12
- medicine side effects
- alcohol or drug misuse
- sleep problems
- head injury, such as a concussion
- blood clots, tumours or infections in the brain
Medicines to review: the NIA lists antihistamines for allergy, sleep aids, antipsychotics, muscle relaxants, medicines for urinary incontinence and medicines for stomach, bowel or bladder cramps as drugs that can impair thinking in older adults. MedlinePlus adds sedatives, some pain medicines and other anticholinergic medicines as causes of confusion. Bring a full list of prescription, over-the-counter and herbal products to the appointment, and do not stop a prescribed medicine without advice.
Hearing and vision loss do not cause dementia, but they can make memory and conversation harder, and the WHO lists both as risk factors for dementia. They are worth checking and correcting.
How is it assessed?
A doctor will ask the person, and ideally a family member or friend, about their health, medicines, daily activities and changes in behaviour. Assessment usually includes:
- short tests of memory, attention, problem solving, counting and language
- blood, urine and other tests to look for other causes
- an assessment of mood, to see whether depression is causing or adding to the symptoms
- a brain scan (CT or MRI) in many cases, to rule out other causes such as stroke or a tumour
Specialist centres may also measure Alzheimer-related proteins in cerebrospinal fluid, on PET scans or, increasingly, in the blood. The NIA advises that a blood test result alone should not be used to diagnose dementia. Availability of these tests varies widely between countries. People with memory problems should be reviewed again every 6 to 12 months.
Red flags: when to get urgent help
- Sudden confusion over hours or days, especially if alertness comes and goes, the person is unusually drowsy or agitated, or talks in a way that does not make sense. This can be delirium, which is often caused by infection (such as a urinary tract infection or pneumonia), medicines, alcohol or drug withdrawal, salt and other body chemical imbalances, or low oxygen. Delirium is usually reversible if the cause is treated. Contact a doctor the same day, or emergency services if the person is very unwell.
- Possible stroke: sudden numbness or weakness of the face, arm or leg (especially on one side), sudden confusion or trouble speaking or understanding, sudden trouble seeing, sudden loss of balance or a sudden severe headache. Use the FAST check (Face drooping, Arm weakness, Speech difficulty, Time to call emergency services). Every minute counts.
- new confusion after a fall or head injury
- confusion with fever or a severe headache, which can mean an infection such as meningitis
- a person with memory problems who is lost, not eating, not looking after themselves or behaving unsafely
Delirium can occur on top of dementia, and the NIA notes that it is frequently followed by cognitive decline. A sudden change in someone with known dementia should be checked, not assumed to be the disease getting worse.
Lowering the risk and planning ahead
No medicine or lifestyle change has been shown to prevent Alzheimer disease. The WHO advises being physically active, not smoking, avoiding harmful alcohol use, eating a healthy diet, staying socially and mentally active, keeping a healthy weight, managing blood pressure, cholesterol and blood sugar, and using hearing aids where needed. Be cautious of supplements and brain-training products that promise to prevent dementia (NIA).
An early diagnosis gives time to plan financial, legal and care decisions, address safety issues such as driving, and consider joining research studies. Most medicines currently available for Alzheimer disease work best in the early or middle stages (NIA).
Frequently asked questions
Is forgetting names a sign of Alzheimer disease?
Not on its own. Forgetting a name or a word now and then and remembering it later is common with age. It is more concerning when memory problems are frequent, getting worse, or interfere with everyday tasks such as paying bills, cooking or finding the way home.
Can depression look like dementia?
Yes. Depression can cause confusion, poor attention and memory problems, and it is also linked to a higher risk of dementia. A doctor should assess mood as part of any memory assessment. Memory often improves when depression is treated.
Is Alzheimer disease inherited?
In most cases there is no single genetic cause. Having a parent or sibling with Alzheimer disease raises the risk, and the APOE e4 gene variant increases risk, but many carriers never develop the disease. Rare variants in three genes (APP, PSEN1 and PSEN2) cause inherited forms that usually start before age 65. The NIA notes that genetic tests are not routinely used to diagnose or predict Alzheimer disease. A doctor or genetic counsellor can discuss family risk.
When should I see a doctor about memory problems?
See a doctor when memory or thinking changes are noticeable to you or others, are getting worse, or affect daily life, and seek urgent care for any sudden change. If stress or low mood seems to be the cause and problems persist beyond a few weeks, book a review.
Sources
- US National Institute on Aging. What Are the Signs of Alzheimer's Disease? nia.nih.gov
- US National Institute on Aging. Memory Problems, Forgetfulness, and Aging. nia.nih.gov
- US National Institute on Aging. Cognitive Health and Older Adults. nia.nih.gov
- US National Institute on Aging. Alzheimer's Disease Genetics Fact Sheet. nia.nih.gov
- US National Institute on Aging. How Is Alzheimer's Disease Diagnosed? nia.nih.gov
- World Health Organization. Dementia, fact sheet. who.int
- US Centers for Disease Control and Prevention. About Alzheimer's Disease. cdc.gov
- MedlinePlus Medical Encyclopedia. Delirium. medlineplus.gov
- MedlinePlus. Stroke. medlineplus.gov
This article is for education and does not replace an assessment by a doctor who knows the person's history. Anyone with sudden confusion or stroke symptoms needs emergency care.
