Mixed dementia

Mixed dementia means a person has brain changes from more than one cause of dementia at the same time. The most common mix is Alzheimer's disease plus damage to the brain's blood vessels.^1,3

This matters because mixed dementia is not rare. In people over 65, and especially in people in their 90s, it may be the usual picture rather than the exception.^2,4 Knowing this can help you ask better questions about diagnosis, treatment and what to expect.

What "mixed" means

Dementia is not one disease. It is a group of brain conditions that harm memory, thinking and daily life. Each type leaves its own changes in the brain:

• Alzheimer's disease: amyloid (a sticky protein that builds up between brain cells) and tau (a protein that forms tangles inside cells). See Alzheimer's disease.
• Vascular changes: strokes, many tiny strokes, or slow damage to small blood vessels. See vascular dementia.
• Lewy bodies: clumps of a protein called alpha-synuclein. See Lewy body dementia.
• TDP-43: another protein that can build up in memory areas. This is called LATE.

In mixed dementia, two or more of these are present together.² Common mixes include:^1,7

Researchers also use the name "multiple-etiology dementia." Etiology means cause.²

How common is it?

Most of what we know comes from brain donation. Scientists study the brains of people who agreed to donate them after death. They then compare what they find with the diagnosis the person had in life.

In one U.S. brain donation study funded by the National Institute on Aging, about 94 out of 100 people with dementia had been told they had Alzheimer's. But when their brains were studied, more than half of those with Alzheimer's (54%) had another cause too. Blood vessel damage was the most common extra cause. Lewy bodies came second.¹

The National Institute of Neurological Disorders and Stroke (NINDS) now says most dementia in people 65 and older is mixed.²

Why it is so common in very old age

The older we get, the more chances there are for several brain changes to build up. The 90+ Study in California followed 183 people in their 90s and studied their brains after death. About 45 in 100 people with dementia had more than one kind of brain change. Among those without dementia, it was about 14 in 100.⁴

In that study, people who had Alzheimer's changes and also had a second kind of change were about four times more likely to have dementia than those with Alzheimer's changes alone.⁴

LATE is another big part of the picture after age 80. In brain studies of more than 6,000 donors, with an average age at death of 88, about 40 in 100 had LATE changes. Just over half of those also had Alzheimer's changes.⁷

Signs and symptoms

The symptoms depend on which brain changes are present and where they are. Often, mixed dementia looks just like Alzheimer's. Sometimes there are clues that more than one thing is going on.¹

Signs that may point to a mix:⁶

• Memory loss plus early trouble with planning, focus or judgment. Blood vessel damage often hits these skills first.
• Sudden drops, rather than a smooth, slow slide. A step-like pattern can follow small strokes.
• More trouble with attention than you would expect from memory loss alone.

Lewy body changes may add other signs, such as seeing things that are not there or acting out dreams in sleep. If you see these, tell the doctor and read the Lewy body dementia page, which explains important medicine safety issues.

How doctors look for it

Mixed dementia is rarely diagnosed during life. Most people later found to have it were told they had one type, usually Alzheimer's.¹ There is no single test for it. Doctors put together several pieces:

• Treatable causes first. Doctors check blood and other tests for problems like low vitamins or thyroid trouble that can look like dementia.³ See treatable conditions that look like dementia.
• Memory and thinking tests. These show which skills are affected, such as memory, planning or attention.³ See memory and thinking tests.
• Brain scans. A CT or MRI scan can show old strokes, bleeding or damage to small blood vessels.^3,6 See brain scans.
• Alzheimer's tests. A blood test, spinal fluid test or PET scan can show whether Alzheimer's proteins are present. The first FDA-cleared Alzheimer's blood test (May 2025) measures amyloid and tau in the blood. The FDA says results must be read along with other health information.¹¹ See blood tests for Alzheimer's.

Put together, these can suggest a mix: for example, a positive Alzheimer's test plus an MRI showing small strokes. An Alzheimer's blood test does not look at blood vessels, so a positive result does not rule out vascular damage.

Some causes cannot be seen at all yet. For example, there is no test for LATE in living people as of October 2026.⁷ So doctors often say "probably Alzheimer's, with some vascular changes," or something similar.

Treatment

No medicine is approved by the FDA just for mixed dementia. Doctors usually treat based on the types they believe are present.¹

What about the new anti-amyloid drugs?

Lecanemab (Leqembi) and donanemab (Kisunla) remove amyloid in early Alzheimer's. But mixed dementia can make them a poorer fit.

For lecanemab, expert advice says people should usually not get it if their MRI shows more than 4 tiny bleeds, a lot of small vessel damage, several small strokes or a large stroke. A stroke or "mini-stroke" in the past year, or needing a blood thinner, can also rule it out.¹⁰ These rules exist because blood vessel problems may raise the risk of ARIA, a type of brain swelling or bleeding.

Also, these drugs only target amyloid. If much of a person's decline comes from blood vessel damage or other proteins, removing amyloid may help less. Ask the doctor how much each cause seems to be adding. See are anti-amyloid treatments right for us?

Lowering the risk of more damage

You cannot remove brain changes that are already there. But the blood vessel part of mixed dementia is the part people can most often do something about.

Blood pressure. In the SPRINT MIND study, more than 9,300 adults aged 50 and older at high risk for heart disease were treated to a lower or a usual blood pressure goal. The lower goal cut the risk of mild cognitive impairment (early memory and thinking problems) by about 20%. There were fewer dementia cases too, but that difference could have been chance.⁸ Your doctor will decide what goal is safe for you. People who had a past stroke or diabetes were not part of this study.

Lifestyle. The U.S. POINTER study tested two healthy lifestyle programs for about two years in older adults at risk of decline. Both programs improved thinking. The more structured program, with more support and accountability, helped more. It has not yet shown that it prevents dementia. A longer follow-up is under way.⁹

Other steps that protect blood vessels include not smoking, keeping blood sugar and cholesterol in range, and treating heart rhythm problems. See lower your risk: blood pressure and heart and keeping your brain healthy.

What to expect over time

Mixed dementia can move faster than one cause alone. NINDS notes that having several brain changes is linked with faster decline in thinking and worse outcomes.² In the 90+ Study, more types of brain change went along with more severe dementia.⁴

But every person is different. Some people stay stable for long periods. Others have a sudden drop after a stroke, then level off. The stages of dementia page explains the general path.

Day-to-day care is much the same as for other dementias. Good routines, calm communication, safety at home and support for the caregiver all matter. Start with caring for someone with dementia and preventing falls, since blood vessel damage can affect walking and balance.

When to get help

• Call 911 for signs of stroke.¹² Also call for a serious fall, trouble breathing, or if the person is hard to wake.
• Call the doctor soon if memory or thinking drops quickly over days or weeks, or if new problems appear, such as hallucinations or falls.
• Call or text 988 if you or the person you care for is in emotional crisis or thinking about suicide. Caregivers can call too.
• Ask for a specialist if the diagnosis is unclear. See which specialist to see.

Questions to ask the doctor

• Do you think more than one thing is causing these changes? Which seems biggest?
• What did the MRI or CT show about strokes or blood vessel damage?
• Would an Alzheimer's blood test or other test change our plan?
• Which medicines might help, and what benefit should we expect?
• What blood pressure, cholesterol and blood sugar goals are right for this person?
• Is this person a candidate for anti-amyloid treatment, given the MRI?

Is mixed dementia worse than Alzheimer's alone?

On average, people with more than one cause tend to decline faster and have more severe dementia.^2,4 But averages do not predict one person's path. Treating blood vessel risks may help slow the vascular part.

Can a person have mixed dementia and not know it?

Yes. Most mixed dementia is not named during life. Many people diagnosed with Alzheimer's are later found to have other brain changes too.¹ This does not mean the first diagnosis was careless. Today's tests cannot see every cause.

Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.