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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141 comments

My mum had been diagnosed with early onset dementia around 5 years ago but I am not sure if she has been diagnosed with a particular form of dementia. My father is very vague on the details and I would like to know if early onset dementia would be followed up with further test to diagnose a particular disease or do we presume it's Alzheimer's. I am very much in the dark with everything and would appreciate a little guidance. Many thanks

Hi Ceri,

Thanks for your comment, and sorry to hear about your mum's diagnosis.

We'd really recommend speaking to one of our dementia advisers for guidance on this, as it's difficult to advise without knowing a bit more information. To do this, you can call our Dementia Connect support line on 0333 150 3456

The support line is open seven days a week:

9.00am to 8.00pm Monday, Tuesday and Wednesday
9.00am to 5.00pm Thursday and Friday
10.00am to 4.00pm Saturday and Sunday.

I hope this is helpful, Ceri.

Alzheimer's Society blog team

My mum got diagnosed with vascular dementia in February this year,,, it has totally thrown my Dad, sister and me into a very scary place. My mum has people round today to say whether it is definite VD, or Alzheimer. We don't know where to go from here, My Dad looks after her he is 80 she is 77,, but we go and help clean and fo shopping and anything else My Dad needs us to do. It's hard to stay strong, as my Mum knows there is something wrong with her head but cannot put her finger on it. The good thing is, that she knows who we all are, so we just need to know who we go through to help us understand things properly, and where to get help when and if we need it, as she is ok at the minute.

Hi Jackie,

Thanks for commenting, and really sorry to hear about your mum's diagnosis.

We would strongly recommend speaking with one of our dementia advisers by calling the Dementia Connect support line on 0333 150 3456. This is a great way to get dementia information, support and advice specific to your situation. (More information about the support line, including opening times, can be found here: https://www.alzheimers.org.uk/dementia-connect-support-line)

You may also benefit from talking with other people affected by dementia within our online community, Talking Point. Feel free to browse and read others' experiences, or create an account to reply and connect with others. You may find similar situations to your mum's shared there: https://forum.alzheimers.org.uk/

We have lots of publications and information about dementia available to read online or you can order free copies in the post. A dementia adviser will be able to help you find the ones that will be most useful for you, or you can browse our full list here:
https://www.alzheimers.org.uk/get-support/publications-factsheets/full-…

Hope this is helpful for you, Jackie. Please don't hesitate to call our support line any time you need advice or support.

Take care,

Alzheimer's Society blog team

My Dad has been diagnosed with Vascular Dementia recently. I haven't seen him for awhile but would like to. What is it like seeing a loved one who has rapidly progressing dementia for the first time? Is there anything I should or shouldn't say? I wouldn't want to upset him but I desperately want to see him before he forgets who I am.

Hi Sarah,

Thanks for your comment.

It's understandable you may be anxious after a long time apart. We have some information on this page (see the section on 'Your reunion') that you may find helpful: https://www.alzheimers.org.uk/get-support/coronavirus/dementia-care-hom…

If you'd like to talk to somebody about your visit first, you can also speak with a dementia adviser by calling our Dementia Connect support line on 0333 150 3456: https://www.alzheimers.org.uk/dementia-connect-support-line

Hope this is helpful, Sarah. Let us know if there's anything else we can help with, and enjoy your visit.

Alzheimer's Society blog team

I am rather concerned about my husband. He will be 77 in September. Sometimes he totally mucks up simple tasks, and other times he is absolutely fine. I thought he was joking when he was saying that I hadn't told him things, but I realise now that he truly doesn't remember. His usual .is sunny and kind, but now, occasionally, he is not very nice, and then he will just go back to being nice again. We do go, together, to the Dr, regularly for our repeat scrips, and if any need arises, so this is good as our Dr has known us for over 12 years, since we shifted to Auckland. His mother had alzeimhers as did my Dad, but I dont know how to recognise the beginnings or simple signs, so I can be aware. Thank you for your time.

Hello Jeanette,

Thank you for getting in touch. We'd recommend speaking with a dementia adviser to discuss your current situation. As you've mentioned you're living in Auckland, you may wish to contact Dementia Auckland (https://dementiaauckland.org.nz/contact-us/) for support. Their freephone telephone number is 0800 4 DEMENTIA / 0800 433 636.

In the meantime, we have some information that may be useful -

> Five things you should know about dementia: Find out the five things that you should be aware of when it comes to dementia. It's not a natural part of ageing and it's not just about memory loss - https://www.alzheimers.org.uk/about-dementia/five-things-you-should-kno…

> Is dementia hereditary? Most dementias are not passed down through the family. This page will help you understand the genetic links for different types of dementia: https://www.alzheimers.org.uk/about-dementia/risk-factors-and-preventio…

> Worried about memory problems? Our new memory booklet is designed to help you understand more about memory loss, dementia, and the next steps to take - https://www.alzheimers.org.uk/memoryproblems

> Normal ageing vs dementia: We explain the difference between normal ageing and dementia, including examples of potential symptoms for three common types of dementia - https://www.alzheimers.org.uk/about-dementia/symptoms-and-diagnosis/how…

> Dementia Talking Point is our online community where anyone who is affected by dementia can receive valuable support. It's free to register, open day or night, and can be accessed online. Explore the community: https://forum.alzheimers.org.uk/

We hope this helps for now, Jeanette.

Alzheimer's Society blog team

I feel confused of late and have been mixing up my words, I feel as if I'm in a sort of fog which doesn't seem to clear? When I'm out with my friends everyone is chatting and laughing and I seem to keep stumbling over what I plan to say but my words don't come out right and I find that people look at me as if I'm not quite right!

Hi Lorraine, thanks for getting in touch and sorry to hear you've been feeling confused.

If you want to talk to somebody about how you've been feeling, you can call our Dementia Connect support line on 0333 150 3456. Find out more about the support line and its opening hours here: https://www.alzheimers.org.uk/dementia-connect-support-line

If you're worried about your memory, it's a good idea to talk to your GP. This page on our website also has some resources which you may find helpful: https://www.alzheimers.org.uk/memoryproblems

I hope this is helpful, Lorraine. Please do call our support line if you would like to talk to one of our Dementia Advisers.

Alzheimer's Society blog team

My parents are both 94 this year my mother has been diagnosed with Alzheimer’s she has basically given up doing anything ,my father has been making tea and toast or a sandwich but I do everything else cooking cleaning washing shopping etc my dad has been getting very disoriented lately and often phones and says he’s somewhere he’s not ( they have been shielding a year) today he phoned my husband to tell him that he and my mum were in Spain running a pub it took us a long time to explain that he’s home ! I have cancer and it’s not curable but I am doing ok I’m also an only child so it all falls on myself and my husband, I don’t even know why I’m writing this just need to vent I think 😀

Sorry to hear your personal news. As with your parents, I am in a similar situation to you and have my own degenerative health issues etc. Sometimes we just need to vent our feelings. There are many times I get frustrated and sad. It’s been hard through lockdown. We’ve had trouble getting support so I’ve been doing all I can to help them. I hear you and I understand you. You take care of yourself too as we have little time to do that and then end up feeling guilty if we do.

My husband was diagnosed with Alzheimer's last year (after much persuasion and eventually given Donepezilo 10 mg.
When and who to I go to, to find out when the medication needs increasing?

Hello Barbara,

We strongly recommend speaking with the GP. We have a helpful factsheet that explains more about how the GP can support people affected by dementia:https://www.alzheimers.org.uk/sites/default/files/pdf/factsheet_how_the…

You can our Dementia Connect support line on 0333 150 3456 if you are in need of general dementia information or emotional support. Our dementia advisers are here for you seven days a week: https://www.alzheimers.org.uk/dementia-connect-support-line

Some people also find it helps to talk with others who have gone through or are going through similar experiences. If you think this would help, you can visit our online community, Talking Point, for peer support: https://forum.alzheimers.org.uk/ It's free and open day or night.

We hope this is helpful.

Alzheimer's Society blog team

Very informative

My Dad has been having a couple of tests as his memory is terrible and he gets letters mixed up when writing simple words like soup. He’s been referred to our local memory clinic and he spoke to the dr last week and he’s told my mum that he has the early signs of dementia. I’m worried about how my Mum will cope if he definitely does have it as he has a bad temper and shouts all the time if anyone says something he disagrees with! so I’m dreading it if he gets any worse as it really upsets my Mum, they’ve been married 50 years this year and love them both to bits!

My 77 year old mum had a fall in May 2020 and broke her right hip causing hospitalisation. It appears this may have caused or accelerated the onset of Alzheimers. She was diagnosed in December with "Dementia in Alzheimers disease with late onset". As Dementia and Alzheimers are different, I am slightly confused myself as to what to expect for her in the future . . .

My friend is saying that her house has fruit fly's . They are on her pillow &. In the kitchen .no other house has them.
She said they are tiny black things.
I asked if they had wings ? She said no, not that she can see.
Her memory is bad , over ten years now.
Is this Lewy bodies ?

Hi Norma,

Thanks for getting in touch. It's hard for us to comment on individual situations as everyone is different. However, if you're worried about your friend's memory problems, we'd recommend seeking advice: https://www.alzheimers.org.uk/memoryproblems

You can also call our Dementia Connect support line to discuss your concerns with one of our trained dementia advisers. They can listen to your friend's situation and provide information and support. Please call them on 0333 150 3456. Opening hours are listed here: https://www.alzheimers.org.uk/dementia-connect-support-line

In the meantime, here's our page on the symptoms of dementia with Lewy bodies, in case this is helpful: https://www.alzheimers.org.uk/about-dementia/types-dementia/dementia-wi…

Alzheimer's Society blog team

My grandfather died a few years back, and he had some form of dementia. The hardest part about it was that he didn't remember me or my sister when we visited him in the care home. His was early onset, so we knew how to cope with things like that. My grandmother would see him twice daily and when he died I think she felt like she had no purpose anymore. We loved her to bits, but we lived far away from them and would only go up at Christmas times and several other holidays. My grandfather remembered music well though, and me and my sister would play music for him every time we went.

My husband is 70 he loses his patience with simple tasks , like opening things, and doing simple daily tasks, he gets frustrated and angry and shouts, do not like him

Hi my wife is 86. .. the doctor says she has Alzheimer’s ,,,, her mobility is getting really bad ... she says she can’t handle every day tasks ,, housework etc ,,, a carer comes in in a morning to help shower and dress her ...what I can’t get my head around is when you read about Alzheimer’s it always mentions memory loss but hers is sharp as a pin past and present she reminds my to do things .... she does suffer from acute anxiety and depression she shuffles and keeps saying “I don’t know what to do “ also takes a memory tablet memenatine also other meds ,,, does anyone else have this type of Alzheimer’s with no memory loss at all thank you mike

my husband has dementia and he is as sharp as ever he knows what he wants but hes lost his speech and mobility, forgets to swallow so dripples a lot.

Thank you for this educative piece. I was not aware of the various diseases that all under 'dementia'.