Dementia and Alzheimer's are not the same thing

Dementia is the umbrella term for a group of symptoms — memory loss, difficulty thinking, trouble with language, and changes in behavior. Alzheimer's disease is one specific cause of dementia, accounting for 60 to 80 percent of dementia cases. Think of dementia as the symptom and Alzheimer's as one of several diseases that can cause it.

When a doctor says someone has dementia, they are describing what is happening — the person is losing cognitive abilities. When they say someone has Alzheimer's, they are naming the disease causing that loss. A person with Alzheimer's will have dementia, but a person with dementia may have Alzheimer's, or they may have a different condition entirely.

This distinction matters because different causes of dementia progress differently, respond to different treatments, and require different planning. Knowing which disease is causing the dementia helps you and your doctor understand what to expect and what steps to take next.

Key Takeaways

  • Dementia describes a set of symptoms including memory loss and difficulty thinking; Alzheimer's is one specific disease that causes dementia.
  • Alzheimer's accounts for the majority of dementia cases, but other conditions like vascular dementia, Lewy body dementia, and frontotemporal dementia also cause dementia symptoms.
  • A diagnosis of dementia means a doctor has confirmed cognitive decline, but additional testing may be needed to identify the underlying cause.
  • Different causes of dementia progress at different rates and may respond to different treatments, so identifying the specific cause matters for planning and care.

Other diseases that cause dementia

Vascular dementia is the second most common cause, occurring when blood flow to the brain is reduced by strokes or narrowed blood vessels. It can develop suddenly after a major stroke or gradually as small strokes accumulate. The pattern of memory loss and thinking problems often differs from Alzheimer's.

Lewy body dementia involves abnormal protein deposits in the brain and often includes hallucinations (seeing or hearing things that are not there) as an early symptom. People with Lewy body dementia may also have movement problems similar to Parkinson's disease.

Frontotemporal dementia typically starts with changes in personality and behavior before memory loss becomes prominent. It often affects younger people — sometimes those in their 40s or 50s — and progresses more rapidly than Alzheimer's.

Other less common causes include dementia related to Parkinson's disease, normal pressure hydrocephalus, and dementia caused by repeated head injuries. Some people have mixed dementia, meaning they have brain changes from more than one disease at the same time.

How doctors tell the difference

A doctor begins by taking a detailed history of when symptoms started, how they have changed, and what the person has noticed. They will ask about family history, past strokes, head injuries, and current medications. They will also perform a cognitive test — a short exam that checks memory, attention, language, and thinking skills.

Blood tests can rule out other conditions that mimic dementia, such as vitamin B12 deficiency or thyroid problems. Brain imaging — usually an MRI or CT scan — can show signs of stroke, shrinkage in specific brain regions, or other structural changes. In some cases, a PET scan can detect the protein buildup characteristic of Alzheimer's.

A diagnosis of Alzheimer's disease during life is technically a diagnosis of probable Alzheimer's, because the only way to confirm it with certainty is through a brain autopsy after death. However, modern imaging and testing make probable Alzheimer's diagnosis quite accurate. If the imaging or symptoms do not fit the Alzheimer's pattern, the doctor will consider other causes.

Why the diagnosis matters for treatment

Medications approved for Alzheimer's disease work by slowing the buildup of proteins in the brain. They do not work the same way for vascular dementia or Lewy body dementia. Some medications that help one type of dementia can actually make another type worse — for example, certain drugs used for Lewy body dementia can be harmful in Alzheimer's.

Treatment also depends on what is causing the dementia. If vascular dementia is the diagnosis, managing blood pressure, cholesterol, and preventing future strokes becomes the priority. If Lewy body dementia is present, doctors will be careful about which medications to avoid because some can trigger severe reactions.

Beyond medication, knowing the cause helps with planning. Frontotemporal dementia often progresses faster and may affect a younger person's work and family responsibilities differently than Alzheimer's would. Vascular dementia may stabilize after the initial stroke but can worsen with future strokes. These differences shape decisions about care, support, and long-term planning.

What happens after a dementia diagnosis

Once dementia is diagnosed, your doctor should discuss what type it is or whether more testing is needed to determine the cause. Ask directly: "Do you think this is Alzheimer's, or do we need more tests to know?" If the diagnosis is unclear, you can ask for a referral to a neurologist or geriatrician — doctors who specialize in brain diseases and aging.

You will likely receive information about how the condition typically progresses, what symptoms to watch for, and what medications or lifestyle changes might help. This is also the time to discuss legal and financial planning — powers of attorney, advance directives, and long-term care options — while the person diagnosed can still participate in those decisions.

Regular follow-up appointments are important. Symptoms change, new treatments may become available, and the doctor needs to monitor how the person is managing. If new symptoms appear — such as hallucinations, movement problems, or sudden changes in behavior — report them, because they may change the diagnosis or treatment plan.

Questions to ask your doctor

When you receive a dementia diagnosis, write down these questions before the appointment so you do not forget them in the moment:

  • What type of dementia do you think this is, and what testing did you use to reach that conclusion?
  • If the cause is not yet certain, what additional tests might help identify it?
  • Are there medications that might slow the progression, and what are the side effects?
  • What symptoms should I watch for, and when should I call you or go to the emergency room?
  • What changes in daily life should we expect over the next year or two?
  • Should we see a specialist, such as a neurologist or geriatrician?
  • What resources or support groups are available for people with this type of dementia?

Frequently Asked Questions

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

Yes. Mixed dementia — having brain changes from more than one disease — is fairly common, especially in older adults. Someone might have both Alzheimer's changes and vascular changes from strokes, for example. This is one reason why brain imaging and a detailed medical history are important; they help the doctor understand what combination of diseases may be present.

If my parent has dementia but the doctor is not sure what type, should I push for more testing?

It depends on your parent's overall health and what the testing would change. If knowing the specific cause would affect treatment decisions or planning, more testing makes sense. If your parent is very frail or the testing would be stressful, the doctor might recommend starting with what is known and monitoring how symptoms develop. Discuss with the doctor what additional testing could reveal and whether it would change the care plan.

Does dementia always get worse?

Most types of dementia do progress over time, but the speed varies widely. Alzheimer's typically progresses slowly over years. Vascular dementia may stay stable for long periods and then worsen suddenly after another stroke. Some conditions that cause dementia-like symptoms — such as depression or medication side effects — can improve with treatment. This is another reason why identifying the specific cause matters.

Is there a test that can tell me if I will develop Alzheimer's or dementia?

There is no test that predicts whether a healthy person will develop dementia in the future. Genetic tests can show whether someone carries genes associated with higher risk, but carrying the gene does not mean dementia will develop. If you are concerned about memory changes in yourself or a family member, talk to your doctor about what you have noticed and whether an evaluation is needed.

What should I tell family members about the difference between dementia and Alzheimer's?

You might say: "Dementia is what is happening — the memory and thinking problems. Alzheimer's is one disease that causes dementia. It is like the difference between 'fever' and 'the flu.' The fever is the symptom; the flu is one thing that causes it." This helps people understand why the specific diagnosis matters and why treatment may differ from what they have heard about dementia in general.