Cognitive Impairment

Which abilities can be affected

Different causes affect different domains first. Alzheimer's disease usually starts with memory; frontotemporal dementia with behavior or language; Lewy body dementia with attention and visual perception. For memory-focused conditions specifically, see memory disorders.

Stages of cognitive impairment

1. Subjective cognitive decline: you notice changes, but tests are normal. Some people go on to develop MCI.
2. Mild cognitive impairment: measurable decline greater than expected for age, with independence largely preserved. About 10 to 20 percent of people over 65 have MCI. Each year roughly 10 to 15 percent progress to dementia; others stay stable or improve.
3. Dementia (major neurocognitive disorder): decline severe enough to interfere with independence in daily activities. It progresses from mild to moderate to severe. See dementia.

Causes

Neurodegenerative diseases

• Alzheimer's disease: the most common cause, with amyloid and tau protein changes.
• Lewy body dementia and Parkinson's disease dementia: fluctuating attention, visual hallucinations, movement problems and sleep behavior disorder.
• Frontotemporal dementia: personality, behavior or language changes, often before 65.

Vascular causes

Strokes and small vessel disease from high blood pressure, diabetes and smoking cause vascular dementia, often with slowed thinking and stepwise decline. Mixed Alzheimer's and vascular disease is common.

Potentially reversible or treatable contributors

• Depression and anxiety
• Medicines: sedatives, sleeping pills, anticholinergics, opioids, some anti-seizure drugs
• Vitamin B12 deficiency and, less often, thiamine or folate deficiency
• Underactive thyroid
• Obstructive sleep apnea and poor sleep
• Hearing and vision loss
• Alcohol misuse
• Normal pressure hydrocephalus: thinking problems, shuffling gait and urinary incontinence
• Brain tumors and subdural hematomas
• Infections: HIV, syphilis
• Organ failure: kidney or liver disease

Acute confusion (delirium)

Delirium is a sudden, fluctuating disturbance of attention and awareness, caused by infection, dehydration, medicines, surgery or other illness. It is a medical emergency and often reversible, though it can unmask or speed up underlying dementia.

Other causes

Traumatic brain injury, chemotherapy ("chemo brain"), long COVID, multiple sclerosis and lupus can affect cognition at any age. Intellectual disability is a lifelong developmental condition rather than a decline.

Risk factors

Age is the strongest risk factor. Others, many modifiable, include high blood pressure, diabetes, smoking, physical inactivity, obesity, depression, hearing loss, social isolation, low education, head injury, heavy alcohol use and air pollution. Research estimates that a substantial share of dementia risk is linked to these modifiable factors.

Diagnosis

1. History from the person and someone who knows them well: what changed, when and how fast.
2. Cognitive screening tests: such as the Mini-Cog, MoCA or MMSE.
3. Physical and neurological examination, including hearing, vision, gait and mood.
4. Medicine review.
5. Blood tests: blood count, B12, folate, thyroid, kidney and liver function, calcium, glucose; sometimes HIV and syphilis tests.
6. Brain imaging: MRI or CT to look for strokes, tumors, hydrocephalus and patterns of shrinkage.
7. Detailed neuropsychological testing to map strengths and weaknesses.
8. Biomarkers in selected cases: amyloid PET scans, spinal fluid tests or newer blood tests for Alzheimer's disease, especially when considering anti-amyloid treatment.

Treatment

• Treat reversible causes: correct deficiencies, adjust medicines, treat depression, sleep apnea and thyroid disease, fit hearing aids.
• Control vascular risks: blood pressure, diabetes, cholesterol, smoking.
• Medicines for Alzheimer's and related dementias: cholinesterase inhibitors (donepezil, rivastigmine, galantamine) and memantine can modestly help symptoms. Anti-amyloid antibody treatments may slow early Alzheimer's disease in carefully selected patients, with monitoring for brain swelling and bleeding.
• Cognitive rehabilitation and stimulation: structured activities, memory aids and routines.
• Physical exercise, which benefits cognition and mood.
• Support and planning: driving safety, finances, legal planning (power of attorney), home safety, and support for caregivers.

Living with cognitive impairment

Keep routines, use calendars and reminders, stay physically and socially active, and involve family early. People with MCI can continue to work and live independently in many cases. Regular follow-up every 6 to 12 months tracks any change.

Frequently asked questions

What is the difference between cognitive impairment and dementia?

Cognitive impairment is a broad term for any decline in thinking abilities. Dementia is the more severe end, where the decline interferes with independence in daily life. Mild cognitive impairment sits in between: changes are measurable, but people still manage most daily tasks themselves.

Does mild cognitive impairment always turn into dementia?

No. Each year about 10 to 15 percent of people with MCI progress to dementia, but many stay stable for years and some improve, particularly when a treatable cause such as depression, medicines or sleep apnea is addressed.

What are the early signs of cognitive impairment?

Early signs include forgetting recent conversations or appointments, repeating questions, trouble finding words, difficulty following complex tasks or managing money, getting lost, and changes in mood or judgment. Family members often notice before the person does.

Can cognitive impairment be reversed?

Sometimes. Impairment caused by depression, medicines, vitamin B12 deficiency, thyroid problems, sleep apnea, alcohol, delirium or normal pressure hydrocephalus can improve with treatment. Decline from Alzheimer's disease and other neurodegenerative conditions cannot be reversed, but can sometimes be slowed.

What tests diagnose cognitive impairment?

Doctors start with a history and short cognitive tests such as the MoCA or Mini-Cog, then blood tests and a brain scan. Detailed neuropsychological testing measures specific abilities. Biomarker tests for Alzheimer's disease may be used in specialist clinics.