Types of dementia: what they are, how they differ and what changes in a session

"Dementia" is not a disease. It is the name for a group of signs (loss of memory, language, orientation, independence) that several different diseases can cause. The main types of dementia are Alzheimer's disease, vascular dementia, dementia with Lewy bodies, frontotemporal dementia and mixed dementia, when there is more than one cause at the same time. There are other, less frequent ones, such as Parkinson's disease dementia or alcohol-related dementia. And mild cognitive impairment, often confused with them, is not dementia.

Knowing which one lies behind it changes what to expect, what to do and what to avoid. This guide brings together the most frequent types, the first signs of each and what sets them apart, and then what each one changes in a virtual reality session. It does not replace a medical assessment: diagnosis always belongs to a doctor, usually in neurology or psychiatry, and depends on tests no article can carry out.

How many people live with dementia

According to the World Health Organization, 57 million people were living with dementia worldwide in 2021, with nearly 10 million new cases every year. It is now the seventh leading cause of death globally and one of the main causes of dependency among older people. It is not confined to old age: young-onset dementia, starting before 65, accounts for up to 9% of cases.

In Portugal, Alzheimer Portugal estimates that 238,401 people were living with dementia in 2025, 2.29% of the population, above the European average (1.77%). The projection for 2050 is almost 368,000.

The most common types of dementia, side by side

Alzheimer's disease

The most frequent cause of dementia. It results from a build-up of abnormal proteins in the brain (beta-amyloid plaques and tau tangles), which progressively damage and destroy nerve cells, often starting in the hippocampus, the area involved in laying down new memories.

First signs. Memory for recent events fails before older memory: the person repeats the same question, forgets yesterday's conversation, yet remembers the village where they grew up in detail. Then come difficulties finding words, finding their way in familiar places and managing tasks such as money or medication.

Progression. Slow and steady, usually over several years, through mild, moderate and advanced stages.

Vascular dementia

Caused by reduced blood flow in the brain: a stroke, several small infarcts, or small vessel disease over time. Not everyone who has a stroke goes on to develop dementia. The risk factors are largely those of the heart: high blood pressure, diabetes, cholesterol, smoking.

First signs. More than memory, it is the speed and organisation of thinking that fails: difficulty planning, following a sequence of steps, concentrating and making decisions, sometimes with short spells of sudden confusion. Changes in walking, falls and mood changes are common.

Progression. Often stepwise: periods of stability interrupted by sudden worsening, which may coincide with new damage. Variation within a single day can also be large.

Dementia with Lewy bodies

Named after abnormal deposits of a protein (alpha-synuclein) inside nerve cells, the Lewy bodies. It is closely related to Parkinson's disease and shares several of its signs, including difficulty with movement and a higher risk of falls.

First signs. Very vivid visual hallucinations (people, animals), often from early on; marked fluctuations in attention and alertness; Parkinson-like motor signs; and sleep disturbances in which the person "acts out" their dreams, talking or moving.

Progression. Fluctuating: the same person may be lucid in the morning and very confused in the afternoon. It is also a dementia with particular sensitivity to some antipsychotic medicines, which makes a correct diagnosis especially important.

Frontotemporal dementia

It mainly affects the frontal and temporal lobes, the areas linked to behaviour, personality and language. It usually starts earlier than the others, most often diagnosed between 45 and 65, which makes it an important cause of dementia in younger people. It is also the one most likely to run in families.

First signs. It depends on the form:

• in the behavioural variant, personality changes, disinhibition, loss of empathy, apathy, repetitive behaviour or changes in eating;
• in the language variants (primary progressive aphasias), difficulty finding words, understanding what words mean or building sentences.

Memory may remain relatively preserved at first, which often delays diagnosis: the signs are mistaken for depression, stress or "just the way they are".

Mixed dementia

At older ages it is common to have more than one cause at the same time. The most frequent combination is Alzheimer's disease with vascular dementia, but there are others, such as Alzheimer's with Lewy bodies. The signs blend, and it can be hard to tell how much each cause contributes.

Other, less common types

• Parkinson's disease dementia: when motor symptoms come first and dementia appears years later. According to the Alzheimer's Society, around a third of people with Parkinson's eventually develop dementia.
• Alcohol-related dementia (alcohol-related brain damage, including Korsakoff syndrome, from vitamin B1 deficiency). Unlike most dementias, it does not always get worse over time.
• Huntington's disease: inherited, with involuntary movements and behavioural changes.
• Creutzfeldt-Jakob disease: very rare and progressing very quickly.
• Repeated head injuries and some infections, such as HIV.

When it looks like dementia but is not

Some conditions cause similar signs and can be treated. It is one of the reasons a medical assessment is essential:

• Delirium: sudden confusion, often from an infection (urinary, respiratory), dehydration or medication. It appears over hours or days, not months.
• Depression in older people, which can mimic memory loss.
• Vitamin B12 deficiency and thyroid problems.
• Side effects of medicines, especially when several are combined.
• Normal pressure hydrocephalus: changes in walking, incontinence and slowed thinking.

And there is mild cognitive impairment, which is not dementia: memory or thinking difficulties greater than expected for age, but not yet affecting everyday independence. It does not always progress to dementia, and sometimes has a treatable cause. We wrote about it in Mild cognitive impairment: usable first, useful after.

If forgetfulness keeps recurring, gets worse and starts to interfere with daily life, the right step is to talk to a GP.

What changes in a virtual reality session

In this sector's marketing material, "dementia" almost always appears in the singular. Anyone working in an activity room knows it is not like that: what works with one person may be irrelevant to another and uncomfortable for a third, and the diagnosis explains part of that.

None of this is ours to decide: the decision always belongs to the clinical team, who know the person. What follows is what tends to change in practice, so that the conversation with whoever is offering technology can be better informed.

In a session: Alzheimer's disease

The most common, and the one with the most literature on non-pharmacological activity. Memory for recent events deteriorates before older memory, which makes reminiscence the most natural territory: childhood places, the home town, the familiar sea.

In practice: old and familiar content before new content. A generically beautiful landscape usually yields less than a place with personal history, and biography is worth more than any catalogue. We have written in detail about Alzheimer's.

In a session: vascular dementia

Two features change the planning. Progression is often stepwise rather than a steady decline: stable periods and abrupt drops. And variability within a single day can be large.

In practice: what went well last week may not this week, and that is nobody's failure. Worth logging the session rather than trusting the shift's memory, so the team sees the pattern instead of guessing it. Motor impairment is frequently associated, which makes position (stable seated, or lying-down mode) more important than in other cases.

In a session: frontotemporal dementia

The one that least matches the stereotype. It often starts earlier, sometimes before 65, and what changes first is behaviour, language or social judgement, not necessarily memory.

In practice: the person may understand perfectly and still refuse abruptly, or lose interest halfway through without warning. That is not negotiated. It is also the population where it is easiest to misread signals: a flat reaction does not mean nothing is happening, and an intense one does not mean discomfort. And since many of these people are younger, reminiscence content "for older people" is inappropriate: the biography belongs to another generation.

In a session: Lewy body dementia, and here caution is greater

This deserves its own section, because it has features that interact directly with what an immersive experience does.

Visual hallucinations are frequent and part of the picture, often from early on. There are also disturbances of visual perception and visuospatial processing, marked fluctuations in alertness through the day, and frequently parkinsonian motor signs.

Placing an immersive display in front of someone whose visual perception is altered is not a neutral decision. We have no evidence of harm, and equally no evidence of safety in this population: what exists is reason for added caution and for the decision to be made by whoever knows the case, with close observation and short sessions, if at all. The neuroleptic sensitivity that characterises this dementia is unrelated to this, but it is a reminder that this is a picture where reactions depart from the expected.

If there is one sentence to take from this article: a supplier presenting virtual reality as good for "dementia" without distinguishing Lewy body has not studied the subject.

What is common to all

• The person, not the diagnosis, decides the content. Diagnosis helps anticipate; biography chooses (the life story form helps gather it).
• Short sessions, shorter than in other contexts.
• Someone familiar alongside, talking. The voice is part of the session.
• Stop at the first sign, and refusal is not negotiated.
• Log what was observed in the words of what was seen, not in conclusions.

What RVer does not do

Worth being explicit: it does not assess, classify or diagnose. It does not distinguish types of dementia, does not suggest content based on diagnosis, and does not measure response. The AI-assisted feature helps find a scenario from the kind of moment the team describes, and the choice always belongs to the team.

RVer is a Class I medical device (registered in EUDAMED, Basic UDI-DI 56006195127RVERTZ, and with INFARMED in Portugal, CDM 94571546), used as a non-pharmacological complement and always under the team's supervision. It does not treat any type of dementia or replace medical care. What is described here refers to the base product; modules in development are not covered.

And the literature, which we gathered in the library, is mostly about wellbeing and reminiscence in mild to moderate dementia. For advanced stages, and for Lewy body in particular, it is thin.

In short

• "Dementia" is a group of signs with several causes, and the cause changes what to expect. In the singular, it is a commercial simplification.
• Alzheimer's: the most common (60 to 70% of cases); starts with recent memory. In a session: reminiscence, old and familiar content.
• Vascular: slowed thinking and difficult planning; stepwise progression. In a session: log rather than trust memory.
• Frontotemporal: behaviour or language first; starts earlier. In a session: abrupt refusal, a different generation's biography.
• Lewy body: visual hallucinations and fluctuations. In a session: greater caution, and no evidence of safety in this population.
• Mixed: frequent at older ages, mostly Alzheimer's with vascular.
• Mild cognitive impairment is not dementia, and some treatable conditions mimic it. Diagnosis is always medical.

Sources

• World Health Organization, Dementia, fact sheet.
• Alzheimer Portugal, press release of 20/07/2026 (prevalence in Portugal, 2025 and 2050; in Portuguese).
• NHS, Causes of dementia.
• Alzheimer's Society, Types of dementia.