Dementia is the umbrella; Alzheimer's is one disease under it

Dementia is not a disease itself — it is a group of symptoms that happen when brain cells stop working or die. Those symptoms include memory loss, trouble with language, difficulty making decisions, and changes in mood or behavior. Many different diseases can cause dementia.

Alzheimer's disease is one specific disease that causes dementia. It accounts for 60 to 80 percent of dementia cases. But other diseases cause dementia too: vascular dementia (from stroke or blocked blood vessels in the brain), Lewy body dementia, frontotemporal dementia, and others. A person with Parkinson's disease or Huntington's disease can also develop dementia as part of that condition.

Think of it this way: all Alzheimer's disease causes dementia, but not all dementia is Alzheimer's. Knowing which one a person has matters because the diseases progress differently, respond to different treatments, and need different kinds of support.

Key Takeaways

  • Dementia is a set of symptoms (memory loss, confusion, behavior changes) caused by damage to brain cells; Alzheimer's is one specific disease that causes those symptoms.
  • Alzheimer's accounts for most dementia cases but is not the only cause — vascular dementia, Lewy body dementia, and frontotemporal dementia are other common types.
  • A doctor must run tests to find out which disease is causing the dementia, because each one progresses and responds to treatment differently.
  • Some people have more than one type of dementia at the same time, which is called mixed dementia and affects how the disease unfolds.

How doctors tell the difference

A doctor cannot tell which disease is causing dementia just by talking to a patient. They need to rule out other causes first — low thyroid, vitamin B12 deficiency, depression, and medication side effects can all look like dementia but are reversible.

Once those are ruled out, the doctor will order brain imaging: usually an MRI or CT scan. These show whether there is damage from stroke (vascular dementia), shrinkage in certain brain regions (Alzheimer's or frontotemporal), or other patterns. A PET scan can sometimes show the buildup of amyloid and tau proteins that are the hallmark of Alzheimer's, but not all doctors order this.

The only way to know for certain that someone had Alzheimer's is through a brain autopsy after death. During life, doctors make a diagnosis based on the pattern of symptoms, the imaging results, and how the disease progresses over time. This is why a diagnosis sometimes changes as new information comes in.

The main symptoms that differ between types

Alzheimer's typically starts with memory loss — a person forgets recent conversations, repeats questions, or loses track of where they put things. Over time, language becomes harder and judgment declines. In later stages, a person may not recognize family members.

Vascular dementia often comes on more suddenly, sometimes after a stroke the person knew they had. The symptoms depend on where in the brain the blood vessels are blocked. A person might have trouble with planning or movement on one side of the body while memory stays relatively intact early on.

Lewy body dementia causes visual hallucinations (seeing things that are not there) early on, along with movement problems similar to Parkinson's disease. Frontotemporal dementia often starts with personality or behavior changes — a person becomes withdrawn, inappropriate, or loses empathy — before memory is affected.

These differences matter because they tell a doctor what to expect and how to plan care. A person with Lewy body dementia, for example, should not take certain antipsychotic medications that can be dangerous for them, while those medications might be considered for other types.

How each disease progresses

Alzheimer's typically progresses slowly over 8 to 10 years, though some people decline faster and others slower. It moves through three stages: early (mild), middle (moderate), and late (severe). In the early stage, a person can usually still live independently with reminders. By the late stage, they need help with all daily activities.

Vascular dementia can progress in steps — a person stays stable, then has a small stroke and suddenly gets worse, then stays stable again. This stepwise pattern is different from Alzheimer's gradual decline. The speed depends on how many strokes happen and where.

Lewy body dementia often progresses faster than Alzheimer's, and the hallucinations and movement problems can make it harder to manage at home. Frontotemporal dementia varies widely — some people decline quickly, others over many years — but behavior problems often make it harder to care for someone even in earlier stages.

Mixed dementia — when a person has two or more types at the same time — is common in older adults. Someone might have both Alzheimer's and vascular dementia, which can make the disease progress unpredictably and symptoms harder to predict.

What treatments are available for each type

Medications for Alzheimer's (donepezil, rivastigmine, galantamine, and memantine) slow memory loss in some people but do not stop the disease. They work by protecting brain cells from damage. These medications are not typically used for other types of dementia, though memantine is sometimes tried.

For vascular dementia, the focus is on preventing more strokes: blood pressure medication, blood thinners if needed, and lifestyle changes like diet and exercise. Treating the underlying vascular disease can slow decline.

Lewy body dementia has no disease-slowing medication, but doctors focus on managing hallucinations and movement problems carefully, avoiding medications that make things worse. Frontotemporal dementia also has no specific treatment, so care centers on managing behavior and supporting the person and family.

All types benefit from cognitive stimulation, physical activity, speech therapy, and occupational therapy. A person with any type of dementia should see a neurologist or geriatrician who can monitor which disease they have and adjust treatment as it progresses.

When to see a doctor about memory or thinking changes

Not every memory slip is dementia. Forgetting where you put your keys or the name of an acquaintance is normal aging. But if a person or their family notices that memory loss is getting worse over weeks or months, or if thinking, language, or behavior is noticeably different, it is time to see a doctor.

See a doctor sooner if memory loss is affecting daily life — a person cannot manage money, forgets to take medications, gets lost in familiar places, or repeats the same question many times in one conversation. These are signs that something needs to be checked.

Bring a list of all medications and supplements, because some can cause memory problems. Bring someone who knows the person well — a spouse, adult child, or close friend — because they can describe changes the person themselves might not notice or might downplay.

Questions to ask your doctor

If a doctor suspects dementia, ask: "What tests will you do to find out what is causing this?" and "How long will it take to get results?" Ask whether they will refer you to a neurologist or if they will manage the diagnosis themselves.

Ask: "What does this diagnosis mean for the future?" and "How fast do you expect this to progress?" Ask about medications — which ones might help, what side effects to watch for, and how often the doctor will check whether they are still working.

Ask: "What should we do now to prepare?" This opens the door to conversations about advance directives, power of attorney, and long-term care planning. Ask about support groups and resources for the person and the family.

Frequently Asked Questions

Can someone have both Alzheimer's and another type of dementia at the same time?

Yes. Mixed dementia is common, especially in people over 80. Someone might have both Alzheimer's and vascular dementia, or Alzheimer's and Lewy body changes. This can make symptoms harder to predict and the disease progress unevenly. A doctor may suspect mixed dementia if the pattern of symptoms does not fit one disease neatly.

If someone is diagnosed with dementia, does that always mean it is Alzheimer's?

No. A dementia diagnosis means brain cells are being damaged and causing symptoms, but it does not say which disease is doing the damage. Testing and the pattern of symptoms over time help narrow it down. Some people are told "dementia, cause unknown" if testing does not point clearly to one disease.

Can dementia be reversed or cured?

Some causes of dementia-like symptoms are reversible — low thyroid, vitamin deficiency, depression, or medication side effects. Once those are ruled out, the underlying disease (Alzheimer's, vascular dementia, etc.) cannot be cured, but medications and lifestyle changes can slow decline in some cases.

Why does it matter which type of dementia someone has?

It matters because each disease progresses differently, responds to different treatments, and needs different kinds of support. Someone with Lewy body dementia should avoid certain medications that are safe for Alzheimer's. Someone with vascular dementia benefits from stroke prevention. The diagnosis helps a doctor and family plan realistic care.

Should someone with dementia see a neurologist or their regular doctor?

A neurologist can do more detailed testing and is trained to spot the differences between types of dementia. A regular doctor can manage early dementia and refer to a neurologist if the diagnosis is unclear or the disease is progressing unusually. Many people see both — their regular doctor for overall health and a neurologist for the dementia itself.