What is the difference between dementia and Alzheimer’s disease?

Dementia is a condition where problems with memory or other types of thinking make it hard for a person to do everyday activities by themselves. It can be caused by several different diseases that affect the brain. Alzheimer’s disease is the most common cause of dementia.

Alzheimer’s disease starts in the brain many years before symptoms start to show. Early symptoms are mild and so don’t stop someone doing their normal everyday activities. It’s only later that symptoms become severe enough to be called ‘dementia’. 

Other common causes of dementia include vascular disease, which prevents blood from getting to the brain properly, and Lewy body disease.

Just as with Alzheimer’s, these diseases develop in the brain over many years. Eventually they lead to vascular dementia and Lewy body dementia.

What is dementia?

Dementia is a group of symptoms. It’s caused by different diseases that damage the brain. The symptoms get worse over time and include: 

  • memory loss 
  • confusion and needing help with daily tasks 
  • problems with language and understanding  
  • changes in behaviour. 

Dementia is progressive, which means symptoms may be relatively mild at first, but they get worse over time.  

What is Alzheimer’s disease?

Alzheimer’s disease is the most common cause of dementia. About two out of three people living with dementia in the UK have Alzheimer’s disease, which is sometimes called “Alzheimer’s”.
Alzheimer’s disease is a physical illness which damages a person’s brain. It starts many years before symptoms start to show.
Early symptoms of Alzheimer’s are mild and don’t prevent someone from doing everyday activities by themselves. This is called mild cognitive impairment (MCI).

It’s often not possible at this stage to say for sure that the person’s symptoms are being caused by Alzheimer’s disease, as there could be many other causes.
Eventually Alzheimer’s disease causes so much damage to the brain that the person develops dementia. Technically this type of dementia is called ‘Alzheimer’s disease dementia’. However, most people – including healthcare professionals – just call it ‘Alzheimer’s disease’.
For most people, Alzheimer’s disease starts in and around the part of the brain involved in memory. However, in some rarer types of dementia the disease starts in a different part of the brain and so causes a different set of symptoms. This is called ‘atypical Alzheimer’s’. For example, posterior cortical atrophy is caused by Alzheimer’s in the back of the brain and mostly causes problems with vision.  

What causes Alzheimer's disease

The causes of Alzheimer’s disease are very complex, but one key part is the build-up of two substances inside the brain called amyloid and tau. When conditions in the brain aren’t right, these clump up and form tiny structures called plaques and tangles. These make it harder for the brain to work properly. 

Over time the disease causes certain parts to become smaller. It also reduces the amount of important chemicals needed to send messages around the brain. 

There is currently no cure for Alzheimer’s disease. However, treatments may temporarily ease some symptoms or slow down their progression in some people. 

What are the main other types of dementia – and what causes them? 

Vascular dementia: this the second most common type of dementia. It is caused by problems with the blood supply to parts of the brain.

Lewy body dementia: Lewy bodies are tiny clumps of protein that build up in the brain. When this happens, it leads to Lewy body disease. There are two main types: 

  • Dementia with Lewy bodies:  When the first signs of Lewy body disease are symptoms of dementia, this is known as ‘dementia with Lewy bodies (DLB)’. 
  • Parkinson’s disease dementia: Lewy body disease can also cause Parkinson’s disease, which mostly involves problems with movement but can also lead to dementia several years later. If it does, this is known as Parkinson’s disease dementia. 

Frontotemporal dementia: this is a less common type of dementia. It can be caused by several different types of disease but they all mostly affect the front or the sides of the brain, known as the frontal and temporal lobes.
Mixed dementia: A diagnosis of mixed dementia is generally used when someone has a mixture of clinical symptoms from two or more different types of dementia – for example, if they have symptoms of both Alzheimer’s disease and dementia with Lewy bodies.  

How do I know what type of dementia I have? 

A diagnosis of dementia needs to be made by a healthcare professional who specialises in dementia, usually following a detailed assessment at a local memory service.  

When someone gets a diagnosis of dementia they should ideally be told by the doctor what type they have. This doesn’t always happen though. Sometimes it’s hard to tell what the cause of a person’s dementia is – particularly during the earlier stages.

It’s not always essential to know straight away what the cause of dementia is, but it can help to make better sense of the person’s symptoms and to get the right treatment.  

Does Alzheimer’s Society support people with dementia, as well as Alzheimer’s disease? 

We support anyone who has dementia. We can help guide people with mild cognitive impairment or who are worried about their memory. Find out how Alzheimer's Society can support you. 

We’re a vital source of support, giving help to everyone who needs it today, and hope for everyone in the future. 

This post was first published in July 2018 and most recently updated in February 2023.

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I am 81 and my husband has demtia although he has not been told this by his doctors he is 96 going on 97 and has a tumour on his bladder and his bladder does not empty properly They say as he get so distressed whenhe has ro go to hospital it is best not to put him through the ordeal He does not wany surgery for his tumour and doctord feel it would cause him too much tress anyway, but it is so hard as there is so much he cannot do ie was dress and often no idea where he is,but a lovely guy who l love dearly but its hard hard work Pauline
Please can help me understand Alzheimer's and dementia I got relatives with Alzheimer's and dementia I found it hard to see my relatives with the disease

Hi Janine, 

We are sorry to hear about your relatives. 

We would recommend calling our Dementia Connect support line on 0333 150 3456. You'll be able to speak with one of our dementia advisers who will listen to your situation, and offer specific advice, information, and support.

You can find more details about the support line (including opening hours) here: https://www.alzheimers.org.uk/dementia-connect-support-line.

We hope this helps.

Alzheimer's Society web team

My sister in Texas can't remember anything at all, will she forget she has a baby sister. IAM from Al, use to be a Texan. And she laughs at everything. Is this normal?
My wife was diagnosed with ‘Alzheimer’s’ about 5 years ago. There were signs for 3 or 4 years before we could get her diagnosed. Four weeks ago she experienced the typical stroke symptoms and spent 4 days in hospital. Other than a slight deterioration in her symptoms she is fine but has had about 5 further but lesser episodes. Her dementia is quite bad during mornings and she improves as the day goes on. She cannot do anything any longer and I have to do most things. She’s 74, as I am too. From her hospital discharge papers it would seem likely that she has vascular dementia. If so, is the Alzheimer’s medication Rivastigmine patches any good for her? Any thoughts?
Hello Malcolm. I’m sorry I cannot answer your question but I just wanted to reach out to say I’m so sorry you are both going through this. You seem like such a wonderful husband to look after your wife and be by her side through all of this. Remember if it does get too much though you must reach out for extra help. You can’t do everything, all of the time, it will make you poorly too. Take care and best of luck to you both.
My parent has been prescribed Alzheimer medication although the doctors have said they can’t say for sure if they have Alzheimer’s. Is this normal?

Hi Abigail,

We'd recommend speaking to your parent's doctor about your concerns. Hopefully, they will be able to provide further detail about the medication your parent is on.

You can also call our dementia support line on 0333 150 3456 for support and advice. (More information on opening times: https://www.alzheimers.org.uk/get-support/dementia-connect-support-line).

We hope this helps.

Alzheimer's Society web team

Is there any link between advanced prostate cancer which has spread to bones and lymph notes, with alzheimers?

Hi Christine, thank you for your question. No, there’s no known link between having advanced prostate cancer and risk of getting Alzheimer’s disease. Chemotherapy is known to cause cognitive impairment though (sometimes referred to colloquially as ‘chemo brain’ or ‘brain fog’) and the process of deteriorating can often cause delirium, which can look like dementia but is actually very different. But cancer does not cause Alzheimer’s disease.

If you are worried about the possibility of Alzheimer's disease, we strongly recommend speaking with your local GP or health provider. If you have any questions or concerns, or if you need support, please also know that you can call our dementia support line and speak with a trained dementia advisor on 0333 150 3456. They can find out more about your situation and offer relevant advice and guidance (More information on opening times: https://www.alzheimers.org.uk/dementia-connect-support-line)

We hope this is helpful, Christine.

Alzheimer's Society web team

My mother has two brain surgeries in 1983 for a benign meningioma. Years later, in 2002 (at best I can recall) she developed dementia. She passed in 2006. My father recently passed of Alzheimer's at age 89. My 66 year old brother has recently been told he has the beginnings of Alzheimer's. Could my mom's dementia have been caused by the two brain surgeries? And with losi g two parents and now my brother, what are the odds I will develop it (I'm 64)?

Hi Lisa, we're very sorry to hear about your family’s experiences with dementia. I’m afraid it’s unclear how the meningioma may have affected your mother’s future risk. However, having three close relatives with a dementia diagnosis is often considered to be suggestive of a possible genetic susceptibility to dementia. It sounds as if you may be based in the US, so the best resource for more information on this would be the Alzheimer’s Association webpage “Is Alzheimer’s Genetic?”. This explains how certain genes can contribute to dementia risk – either rare gene mutations that always cause dementia if inherited from a parent (known as ‘familial dementia’) or much more common ‘risk genes’, such as APOE-e4, that just increase the likelihood of getting dementia. The AA resources will then be able to direct you to testing facilities near you, should you need them.

We hope this helps, Lisa.

Alzheimer's Society website team

Can undiagnosed Giant Cell Arteritis which has progressed to blindness cause vascular dementia in the same side as the infection?

Hi Elizabeth,


In this case, we'd recommend speaking to a medical professional such as a GP about your concerns. They will be able to provide you with specific information that's relevant to your situation.

If you need support, please also know that you can always call our dementia support line on 0333 150 3456. (More information on opening times: https://www.alzheimers.org.uk/get-support/dementia-connect-support-line)

We hope this helps, Elizabeth.

Alzheimer's Society blog team

Has my friends 71yr old father got the early signs of dementia or something else, as a lot of the early symptoms don't apply to him, however these are his symptoms and they only came on over 4/5mths which I think is pretty quick!? - 1. Forgetting where he has put something only hours before. 2. Generally forgetting where things are which he has put. 3. Repeating questions or statements within moments of asking or saying it the first time, especially if it is his drinking night. 4. Starting jobs and not finishing them but starting them on something else leaving half done projects everywhere (he doesn't forget there half done) 5. Pointless tasks for example, he wanted to sort a cupboard out in the garage and get rid of a few things but all he did was pull things out of one cupboard and put them in another cupboard to which he only got rid of 3 light bulbs. He thought it was a job that really needed doing although it was a spare of the moment random thing he came up with and a pointless exercise, the cupboard he moved the stuff into was the cupboard next to it which was exactly the same in every way. Is this dementia the early signs? If not what else could this mental deterioration be?
My mum is 80. She is having difficulty remembering recent events and conversation. More recently also showing confusion. We don't want to over react, and don't know what to do to help. We feel that if we suggest a Dr appointment it will make her angry or upset or both. Any advice welcome
Hi I was in this position with my mother, her short term memory was getting very bad and was confused in what should have been known areas. I did mention it to her and said when you broke your hip you went to see the GP. She was having none of it...... ! I spoke to the GP with my concerns and they wrote to her asking her to make an appointment as they hadn't seen her through covid. She passed the test with flying colours ! However a few more prompts from me she had a scan and was diagnosed with vascular disease. Very difficult as she lives with me and I am constantly helping her. She gets cross and quite nasty. Some days better than others.

My brother was diagnosed with vascular dementia 3 years ago when he was just 68. I always blamed his heavy smoking, not sure if it is related. He is now in a nursing home, it must be awful to lose your home, your independence. His personality has totally changed, from a gentle soul to a very aggressive person. I don't know of anybody else in the family who has had it, and from what I have researched it isn't hereditary. Can the smoking have caused it? Is it hereditary? I am the only person he has, nobody else bothers with him. Not sure why I am writing this, just offloading I think.

Hello Jenny,

We're sorry to hear about your brother's vascular dementia diagnosis.

The causes of dementia are complex, and researchers are working to understand this more clearly. Although was can't say what causes dementia, we know that certain things can increase a person's risk of dementia. We have some information about risk factors for vascular dementia on our website: https://www.alzheimers.org.uk/about-dementia/types-dementia/risk-factor…

If you would like more dementia information, advice, or support, please call our Dementia connect support line on 0333 150 3456. More details of the support line (including opening hours) are available here: https://www.alzheimers.org.uk/dementia-connect-support-line

We hope this helps,

Alzheimer's Society website team

How do I deal with / what do I do say when my mum who has mixed dementia, and is confused of where she is, thinks she’s on holiday and waiting to be picked up, packs things in bags because she thinks she’s going on holiday, things like fruit, butterfish, cello tape,

Hi Delia,

It sounds like you might benefit from joining our online community, Talking Point, where people affected by dementia can share their experiences and ask each other questions. You can browse the conversations within the community or sign up for free: https://forum.alzheimers.org.uk

We hope this helps.

Alzheimer's Society blog team

My wife would appear to be suffering from dementia but has never been diagnosed She contacted covid 14 months ago and had a mild stroke 12 months ago our GP is fully aware of her situation How do I go about getting her diagnosed to confirm what type she is suffering from She has also been diagnosed with breast cancer 2 years ago in June 2020

Hi Percy,

Thanks for your comment, and sorry to hear that your wife is displaying symptoms of dementia.

It's great that you've already spoken to your GP. They may decide that your wife should be assessed for dementia - you can find more information about this process on our website: https://www.alzheimers.org.uk/about-dementia/symptoms-and-diagnosis/dia…

If your wife has not been assessed and you think that she should be, then you may find it helpful to speak with one of our dementia advisers. They will be able to learn more about your situation and give advice. You can call our Dementia Connect support line on 0333 150 3456. More details (including opening hours) are available here: https://www.alzheimers.org.uk/dementia-connect-support-line

I hope this is helpful, Percy. Wishing you all the best.

Alzheimer's Society website team

My mum has just been diagnosed with Alzheimer’s today - she only 74 abs has survived Pancreatic cancer she is a walking miracle- why is life so cruel with her getting this ?
No idea how to manage this - I support her with medication and shopping etc - so worried how it will progress

Hi Pauline,

We are very sorry to learn about your mother's diagnosis. This must be such a worrying time for you and your family. Please know that you aren't alone, and we are here for you.

We'd recommend calling our Dementia Connect support line on 0333 150 3456 and speaking with one of our dementia advisers. They can answer any questions you might have and provide dementia information and support. More details about the support line (including opening hours) are available here: https://www.alzheimers.org.uk/dementia-connect-support-line

Our advisers can also provide you with any reading material that you might find helpful. We have lots of publications and factsheets about dementia - you can download and read online versions, or request copies of resources in the post: https://www.alzheimers.org.uk/get-support/publications-factsheets/full-…

In particular, you might be interested in our booklet Caring for a person with dementia: A practical guide. The information in this booklet is here to support you to care for the person with dementia and to look after yourself: https://www.alzheimers.org.uk/get-support/publications-factsheets/carin…

You might also find it useful to speak to other people who are going through similar situations within our online community, Talking Point. Here, carers and other people affected by dementia share their experiences and offer each other support and advice. It's open day or night, and free to use. Read more about the community, or register to join the conversation: https://www.alzheimers.org.uk/get-support/dementia-talking-point-our-on…

We hope this helps, Pauline. Please do call our support line if you need to speak with an adviser.

Alzheimer's Society blog team


Thank you for providing this informative set of blogs related to ALZHEIMER’S, looks pretty enlightening and effective for individuals suffering from the disease. The content is best for getting information regarding the issue. I was on the look for such info.

We haven't had a diagnosis and indeed, seeing
a doctor at this time is very difficult still.
Concerned about the deterioration of a family member of 83 years old.
Already one member of family takes her shopping and our part look after finances, bills etc. She would be unable to do this independently now. Losing weight, clearly not cooking anymore etc etc. Forgetting medication, repetition all evident.
Short term memory isn't good. So many aspects in descriptions here are ringing alarm bells.
What is our first step? Is it insisting we see a doctor?
Any guidance would be appreciated...
Thank you.

Hi Sara

We're really sorry to hear about your family member - this must be a very worrying time for you.

We would strongly recommend calling our Dementia Connect support line on 0333 150 3456. You'll be able to speak with one of our dementia advisers who will listen to your situation, and offer specific advice, information, and support.

You can find more details about the support line (including opening hours) here: https://www.alzheimers.org.uk/dementia-connect-support-line

You might also like to read through our information on diagnosis, which explains the dementia assessment processes, should you want to learn more about it: https://www.alzheimers.org.uk/about-dementia/symptoms-and-diagnosis/dia…

We hope this helps, Sara. Please do call our support line for advice when you need it.

Alzheimer's Society blog team