The different forms of dementia

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Dementia isn’t a specific illness. Rather, it’s a set of symptoms caused by different diseases that result in the deterioration of brain function. Different types of dementia and their symptoms vary from person to person, but they always go beyond memory loss. The most common form, Alzheimer’s disease, is only one type of dementia. Despite there being rarer types of dementia, here, we’ll explore the more common different forms and what sets them apart from other types. 

If you or someone you know is experiencing any of the below symptoms, we advise that you contact your GP. They can help rule out if you’re experiencing the symptoms due to a form of dementia or if they can be explained by other life factors. They can also signpost you and your loved ones to support and guidance.

Alzheimer’s disease 

What is Alzheimer’s disease? Although the causes are complex, the accumulation of amyloid and tau, two substances in the brain, play a key role in the development of the physical disease. When brain conditions aren’t quite right, these substances clump up and create tiny structures named plaques and tangles, which can make it harder for the brain to function. Gradually, the condition results in parts of the brain shrinking and reduces the number of vital chemicals needed to transmit around the brain for essential body functioning and movement.  

How common is it? In 2019, the Alzheimer’s Society stated research revealed over 850,000 people lived with dementia in the UK and, at that rate, predicted over 1.5 million people will be living with dementia by 2040. Of the 850,000, 50-75% of people are thought to have Alzheimer’s disease. 

Symptoms: Alzheimer’s affects everyone differently, but the disease tends to start as minor memory problems, such as being unable to recall names of places or recent conversations. As the condition develops, a person living with Alzheimer’s may experience:  

• confusion, disorientation and getting lost in familiar places 
• trouble planning or reasoning 
• issues with speech and language 
• difficulty moving around unaided or performing personal-care tasks 
• personality alterations, for example, becoming aggressive, demanding and suspicious of others 
• hallucinations (seeing or hearing things that aren’t there) and delusions (believing things that aren’t true) 
• low mood or anxiety 

Progression: Alzheimer’s disease is a progressive neurological condition, meaning symptoms develop slowly over many years and, in time, becoming more acute. People with Alzheimer’s can live for several years after the onset of symptoms, but this can vary considerably from person to person.  

Vascular dementia

What is vascular dementia? There are various types of vascular dementia, which is caused by a deficiency in blood flow to the brain. These are:

• Stroke-related vascular dementia – caused by a stroke, which happens when blood supply to the brain is abruptly blocked by a clot and narrowed blood vessels or by a bleed (excessive flow). Stroke-induced damage can be permanent or temporary; it depends on where the narrowed blood vessel is and how long the blood supply was disrupted for. However, many people who struggle with their thinking during the weeks and months after a stroke don’t develop dementia. 
   
• Single-infarct and Multi-infarct vascular dementia – occurs thanks to a series of smaller strokes. Should the mini stroke disrupt the brain’s blood supply for more than a few minutes or hours; the mini stroke may result in permanent brain damage. The damaged areas of the brain are referred to as ‘infarcts’. If someone has many small strokes over time, multiple infarcts will accumulate in their brain, which could lead to multi-infarct dementia. 
   
• Subcortical vascular dementia – results from diseases of tiny blood vessels deep in the brain, usually in the part called the ‘sub-cortex’, which helps with the expression and control of emotions and links all the different parts of the brain together, enabling information to be quickly processed. Over time, these blood vessels can form hardened walls and become stiff and twisted, hindering the blood flow through them. The areas of the brain these blood vessels supply then lack oxygen and nutrients, leading to the affected brain cells dying.   

How common is it? The Alzheimer’s Society cites vascular dementia as the second most common type, making up to about 20% of cases of dementia, with the NHS estimating that it affects around 150,000 people in the UK.  
 
Around one in five people develop the stroke-related form of vascular dementia within six months of having a stroke. Meanwhile, subcortical vascular dementia is considered to be the most common type of vascular dementia. 

Symptoms: In the early stages of vascular dementia, people may find it challenging to: 

• plan, organise, problem solve or make choices 
• follow a series of steps like a recipe 
• think quickly 
• concentrate 
• use language 

Someone who experiences damage to the area of the brain that’s responsible for language due to a stroke will see a decline in their language, whereas someone who experiences damage to the area of the brain that controls how emotions are handled will see a problem in regulating emotions. It all depends on which part of their brain their stroke impacted. A stroke can cause physical symptoms too, such as: 

• difficulties with movement and sensation 
• weak limbs 
• speech difficulties 
• problems swallowing 

Progression: Vascular dementia can develop suddenly or gradually over many months and years. Although the symptoms tend to worsen overtime, potentially resulting in shifts in mood, behaviour and personality, confused and disoriented spells, and difficulty walking, it’s sometimes possible to slow the condition down.  

With rehabilitation, symptoms may be alleviated or stabilise for a while, particularly in the initial weeks and months following the stroke. 

Similarities with other types of dementia: The Alzheimer’s Society notes that vascular dementia often co-exists with Alzheimer’s disease.  

Transient ischaemic attacks (TIAs)

What are TIAs? These are like strokes but are more fleeting and typically resolve by themselves. They can be responsible for single-infarct and multi-infarct vascular dementia. 

Progression: Sometimes people may not know that they’ve experienced a TIA. However, if one is suspected, it’s vital it’s investigated rapidly and thoroughly by a medical professional as it’s possible to find the place in the brain where the clots causing the TIA are coming from. The source area can then be surgically treated to significantly reduce the likelihood of future TIAs.  

If you think you’ve had a TIA, it’s essential that you contact your GP, even if your symptoms disappear quickly. Likewise, if someone you know thinks they’ve had a TIA, it’s important you try to encourage them to contact their doctor.

Dementia with Lewy bodies (DLB)

What is dementia with Lewy bodies? Microscopic deposits of proteins known as Lewy bodies develop in the brain’s nerve cells to cause this type of dementia.  

How common is it? Around 10-15% of people who have dementia are thought to have this type.  

Similarities with other types of dementia: Lewy bodies can trigger a variety of symptoms, like those seen in people with Alzheimer’s disease and Parkinson’s disease. Due to these similarities, it can often be misdiagnosed.  

Symptoms: The features of DLB will be partly determined by where the Lewy bodies are in the brain:  

1. If they’re in the base of the brain then they’ll impact movement, which is the main trait of Parkinson’s’ disease. 
2. If they can be found in the outer layers of the brain, they’ll affect mental abilities, a hallmark of DLB and other types of dementia.  

Features of both DLB and Alzheimer’s disease are:  

• Issues maintaining concentration 
• Trouble reasoning 
• Loss of memory 
• Difficulties with seeing and interpreting the surrounding world 

Features of DLB that don’t usually occur in Alzheimer’s include:  

• Disrupted sleep 
• Struggling to stay fully awake 
• Problems moving 
• Hallucinations  

Progression: Typically, DLB develops over several years and the following may arise in the later stages:  

• Difficulty eating and drinking 
• Speech and swallowing challenges may result in chest infections and an increased choking risk
• An increased likelihood of getting upset or distressed 
• Less stability when walking, increasing the chances of falling

Frontotemporal dementia  

What is frontotemporal dementia? This type of dementia is characterised by having damaged nerve cells in the frontal and temporal lobes of the brain. The frontal lobe is located behind your forehead, whilst the temporal lobes can be found on either side of your head nearest your ears.  

As a result of this damage, links between the two sets of lobes and other parts of the brain deteriorate and levels of chemical messengers in the brain also gradually decrease. As more nerve cells die, brain tissue in the two lobes begin to shrink.  

How common is it? This is a less common form, accounting for around 2% of people living with dementia.  

Symptoms: The initial obvious signs of frontotemporal dementia are personality and behaviour changes and / or language troubles. Broadly speaking there are two types of frontotemporal dementia:  

1. Behavioural variant – this is when frontal lobe damage mainly results in behaviour and personality changes and is the most common form of frontotemporal dementia.  
2. Primary progressive aphasia (PPA) – this is when damage to the temporal lobes leads to language difficulties.  

Both types of frontotemporal dementia and their subtypes, such as the semantic variant of PPA and the Non-fluent variant PPA, present their symptoms differently, which you can read more about here.  

Progression: How quickly frontotemporal dementia progresses will vary from person to person, with their age at diagnosis and if they have other health conditions influencing the progression. 

Similarities with other forms of dementia: In the final stages of frontotemporal dementia, the symptoms are akin to the later stages of other types of dementia, such as Alzheimer’s disease. 

Mixed dementia

What is mixed dementia? When a person has more than one type of dementia it’s called ‘mixed dementia’.  

How common is it? Alzheimer’s disease and vascular disease is the most common combination of mixed dementia, although other mixtures are possible, such as Alzheimer’s disease and dementia with Lewy bodies. Despite Alzheimer’s disease and vascular dementia being the two most common types of dementia, relatively few people receive a ‘mixed dementia’ diagnosis. This is because doctors usually only diagnose mixed dementia when a person has clear clinical features of two types of dementia that directly impact symptoms.  

Symptom and progression: The symptoms of mixed dementia will vary depending on the combination a person has. In most cases, someone will have the symptoms of one more ‘predominant’ type of dementia over another. Progression will also depend on what stage they got diagnosed and will vary from person to person.