Dementia is not one disease. It is an umbrella word for a group of brain conditions. Each one makes memory, thinking or daily skills worse over time, enough to get in the way of everyday life.^1,2 Alzheimer's disease is the best known, but there are many other types.

Knowing the type matters. It helps you know what changes to expect. It can also change which medicines are safe and which treatments may help. This page gives a short overview of each type, with links to a full page on each one.

Key points

Dementia is a group of conditions, not a single illness. Alzheimer's disease causes about 60% to 80% of cases.¹
Many older people have more than one cause at the same time. This is called mixed dementia.⁴
The type matters for safety. For example, people with Lewy body dementia can react badly to antipsychotic medicines.⁵
Some memory problems come from treatable conditions, such as thyroid problems, low vitamins, depression or medicine side effects. A good checkup looks for these first.¹
Memory or thinking that gets much worse over weeks or a few months needs a doctor's visit right away.¹⁶

Dementia is not a normal part of aging

Different diseases damage the brain in different ways and in different places.² That is why one person may first lose memory, while another first changes in personality or has trouble with words.

Dementia is not a normal part of aging, but the risk goes up with age. Up to half of people aged 85 or older may have some type of dementia.² Still, forgetting a name now and then is common at any age. Losing the ability to manage money or find your way home is not.

The main types at a glance

Numbers are estimates and vary between studies.

Type	What it often looks like	How common
Alzheimer's disease	Slowly worsening memory for recent events, then trouble with words, planning and finding the way	The most common type. About 60% to 80% of cases.¹ About 7.4 million Americans aged 65 and older live with it in 2026.³
Vascular dementia	Slow thinking, trouble planning, problems after a stroke. May get worse in steps	About 5% to 10% of dementia on its own. Much more common mixed with Alzheimer's.⁴
Lewy body dementia	Big swings in alertness, seeing things that are not there, acting out dreams, stiff or slow movement	About 1.4 million Americans.⁵ Lewy body changes alone are found in about 5% of older people with dementia.⁴
Parkinson's disease dementia	Thinking problems that start years after Parkinson's movement problems	About 3.6% of dementia cases.⁴
Frontotemporal dementia (FTD)	Personality and behavior changes, loss of judgment, less caring or interest. Often starts at 45 to 64	About 60,000 people in the U.S.⁶ About 3% of dementia after 65, and about 10% before 65.⁴
Primary progressive aphasia	Slowly losing language: finding words, speaking, understanding	Rare. Part of the FTD group.²
Mixed dementia	Often looks like Alzheimer's	Very common. More than half of people diagnosed with Alzheimer's at research centers had more than one cause.⁴
LATE	Memory loss that looks like Alzheimer's, mostly after age 80, often slower	Found at autopsy in about 1 in 5 to 1 in 2 people over 80.⁷
Posterior cortical atrophy	Trouble reading, judging distance or seeing several things at once, while the eyes are healthy. Often starts at 50 to 65	Uncommon.⁹
Normal pressure hydrocephalus	Problems walking, bladder control and thinking	Most common in older adults. Can improve with treatment.¹⁰
Creutzfeldt-Jakob disease	Very fast decline in thinking, movement and behavior	Very rare. About 1 to 2 per million people a year.¹¹
Alcohol-related brain damage	Trouble learning new things and remembering recent events	Linked to heavy drinking and low vitamin B1.¹²
Huntington's disease	Uncontrolled movements, mood changes and thinking problems, often in mid-life	Rare. Inherited.¹³
Down syndrome and Alzheimer's	Alzheimer's that starts younger than usual	About 3 in 10 people with Down syndrome in their 50s, and about half in their 60s.¹⁴

The most common types

Alzheimer's disease. Two proteins build up in the brain. Amyloid (a sticky protein) forms clumps between brain cells. Tau (another protein) forms tangles inside them.² Memory for recent events is usually the first thing to change. See Alzheimer's disease.

Vascular dementia. This comes from poor blood flow in the brain, for example after strokes or from damage to tiny blood vessels.² Problems may get worse in steps or slowly over time. See vascular dementia.

Lewy body dementia. Clumps of a protein called alpha-synuclein form inside brain cells.² There are two forms. In dementia with Lewy bodies, thinking problems come first or at about the same time as movement problems. In Parkinson's disease dementia, movement problems come first, often by years.²

Frontotemporal dementia. This affects the front and side parts of the brain, which guide behavior, emotions and language.² It often starts younger than other types. It is the most common dementia in people under 60. It is often mistaken for depression or another mental health condition, and diagnosis takes an average of 3.6 years.⁶ One form, primary progressive aphasia, mainly takes away language.² See frontotemporal dementia.

Mixed dementia. Many older adults have more than one kind of brain change, such as Alzheimer's plus small strokes. In one study of older people thought to have Alzheimer's dementia, only about 3 in 100 had Alzheimer's changes alone.⁴ See mixed dementia.

Less common types

LATE is a brain change involving a protein called TDP-43. It mostly affects people over 80 and looks like Alzheimer's.⁷ In 2025, experts published criteria to help doctors recognize it during life. When LATE occurs alone, it tends to get worse more slowly than Alzheimer's.⁸
Posterior cortical atrophy damages the parts of the brain that make sense of what the eyes see. People often go to an eye doctor first, and a normal eye exam can delay the right diagnosis.⁹
Normal pressure hydrocephalus is a buildup of fluid in the brain. A shunt (a thin tube that drains the extra fluid) can help some people a great deal. Early treatment gives the best chance.¹⁰
Creutzfeldt-Jakob disease is caused by prions (misfolded proteins). It moves very fast and is fatal, usually within a year.¹¹
Alcohol-related brain damage includes Wernicke-Korsakoff syndrome, caused by a severe lack of thiamine (vitamin B1). Treatment includes thiamine, good food and no alcohol. Based on limited data, about 1 in 4 people recover and about half improve.¹²
Huntington's disease is passed down in families. Each child of a parent with the disease has a 50% chance of inheriting it.¹³
Down syndrome and Alzheimer's: People with Down syndrome have an extra copy of chromosome 21. It carries a gene linked to amyloid, which raises the risk of Alzheimer's at a younger age.¹⁴

Mild cognitive impairment is not dementia

Mild cognitive impairment (MCI) means memory or thinking has slipped more than expected for your age, but you can still handle most daily tasks on your own. About 12% to 18% of people aged 60 and older have MCI.¹⁵

MCI does not always lead to dementia. About 10% to 15% of people with MCI develop dementia each year. Some stay the same, and some get better.¹⁵ People with MCI from Alzheimer's may be able to get the newer anti-amyloid medicines, which are only for the early stages of the disease.¹⁷

Why knowing the type matters

Medicines. Medicines like lecanemab and donanemab are for the early stages of Alzheimer's. They were studied in people with tests showing amyloid in the brain.¹⁷ They are not for other types. See dementia medicines.
Safety. Many people with Lewy body dementia have a severe reaction to antipsychotic medicines.⁵ Make sure every doctor and hospital knows the diagnosis. See medicines to avoid.
Planning. Some types start younger or move faster. See stages of dementia and power of attorney.
Family health. A few types, such as Huntington's disease, are passed down in families.¹³ A genetic counselor can explain what testing means. See genetic testing.

Check for treatable causes first

Before calling it dementia, a doctor should look for other problems that can affect memory. Depression, medicine side effects, heavy drinking, thyroid problems and low vitamins can all cause thinking problems that may get better with treatment.¹ Fluid buildup in the brain, a slow bleed on the brain after a fall (subdural hematoma), infections and tumors can also look like dementia.² See treatable conditions that look like dementia.

Fast changes are urgent. If memory, thinking or behavior gets much worse over days, weeks or a few months, see a doctor right away. Some causes of dementia that gets worse fast, such as autoimmune conditions, can be treated.¹⁶ Sudden confusion over hours or a day may be delirium. If someone is suddenly confused, very drowsy, has trouble speaking, or has weakness on one side, call 911.

In this section

Alzheimer's

What Alzheimer's disease does in the brain, early and late onset, symptoms by stage, the new biomarker-based definition, and treatments as of 2026.

Types of dementia

Dementia is not a normal part of aging

The main types at a glance

The most common types

Less common types

Mild cognitive impairment is not dementia

Why knowing the type matters

Check for treatable causes first

In this section

Alzheimer's

Vascular dementia

Lewy body dementia

Parkinson's dementia

FTD

PPA

MCI

Mixed dementia

LATE

NPH

PCA

CJD

Alcohol and the brain

Huntington's

Rapidly progressive dementia

Down syndrome

Dementia look-alikes

When to get help