When Alex Aguzzi’s mother, Anna, was first told she had dementia, the diagnosis was just that: “dementia.” No type, no explanation of what to expect. It took years, and a doctor at Baycrest, before the family learned that Anna was living with Alzheimer’s disease together with Lewy body disease, and before her hallucinations, falls and fears finally made sense. Their story opens Episode 33 of Baycrest’s Defy Dementia podcast, “Dementia 101,” hosted by science journalist Jay Ingram and Dr. Allison Sekuler, President and Chief Scientist of the Baycrest Academy for Research and Education and the Centre for Aging + Brain Health Innovation.

What is dementia?

Dementia is not a single disease. It is a term for a group of symptoms, including problems with memory, thinking and reasoning, that can be caused by many different brain diseases.

Dr. Valerie Sim, a neuroscientist, clinical neurologist and Associate Professor in the Division of Neurology at the University of Alberta, compares it to a headache: a migraine, a knock on the head and a brain tumour can all cause one, but they are very different problems. In the same way, several different diseases can cause dementia.

According to the World Health Organization, Alzheimer’s disease is the most common cause, contributing to 60 to 70% of cases. The boundaries between types are not always clear, and mixed forms often exist together.

What are the main types of dementia?

The four most common types are Alzheimer’s disease, vascular dementia, Lewy body dementia and frontotemporal dementia. Each tends to cause a different pattern of symptoms.

Alzheimer’s disease. The most common early sign is short-term memory loss: repeating questions, or forgetting why you walked into a room. Dr. Sim explains that one of the first areas to shrink is the hippocampus, a part of the brain that files new memories for storage. Older memories are already stored elsewhere, which is why someone may recall events from decades ago but not yesterday. Word-finding problems, trouble using familiar devices and getting lost can follow.

Lewy body dementia. Its hallmark signs include vivid visual hallucinations, often of people or small animals; acting out dreams during sleep; and stiffness, slowness and shuffling like Parkinson’s disease. Thinking and alertness can change from hour to hour. International diagnostic criteria list these as core features, with repeated falls and drops in blood pressure as supporting signs. Memory can be relatively spared early on.

Vascular dementia. This is caused by damage to the blood vessels that supply the brain. Dr. Sim compares it to a tree slowly losing its small branches, so the leaves no longer get what they need. Connections between brain areas are lost and thinking slows. Defy Dementia explores it further in Episode 37: When Blood Meets Brain.

Frontotemporal dementia. This group of diseases affects the front and sides of the brain and can first appear as changes in personality or behaviour. Learn more in Episode 36: Personality Unraveled.

Why do different types of dementia cause different symptoms?

Because each disease involves a different protein going wrong, and each of those proteins damages a different part of the brain.

Proteins only work when they are folded into the right shape. In Alzheimer’s, frontotemporal and Lewy body dementia, certain proteins fold into the wrong shape and then pass that misfolding on to their neighbours, spreading through the brain like falling dominoes. In Alzheimer’s disease, the proteins are amyloid beta and tau. In Lewy body dementia, a protein called alpha-synuclein builds up into clumps called Lewy bodies. Frontotemporal dementia can involve several different proteins.

Where the damage happens shapes the symptoms. Lewy body disease affects areas deep in the brain that control movement, which explains the stiffness and shuffling, and areas at the back of the brain that process what we see, which helps explain the hallucinations.

Can you have more than one type of dementia?

Yes, and it is common. Dr. Sim says one of the most frequent combinations is Alzheimer’s disease with vascular disease, and Lewy body disease often appears alongside other types too.

Brain studies support this. A 2007 study that examined the brains of older adults after death found that mixed disease accounted for most dementia cases among older people living in the community, and that the combination of Alzheimer’s changes and strokes was the most common mix. A 2017 review found that having additional diseases lowers the threshold at which dementia symptoms appear. Often, the full picture is only confirmed by examining the brain after death.

How did Alex recognize her mother’s dementia?

Slowly, and not in the order many people expect. About 20 years ago, Anna began searching for words, which Alex put down to English being her second language.

Anna grew up in Arezzo, in Tuscany, and came to Canada in 1952. Widowed at 48, she reinvented herself as a painter whose oil paintings were exhibited in Toronto’s Yorkville neighbourhood. Over the years, new signs appeared. During a hospital stay for pneumonia in 1999, she saw disturbing images that were not there. Later, the woman who used to walk for miles across the city began losing her balance and falling. After a fall down the stairs in 2019, she developed delirium, a sudden state of severe confusion, before returning to herself days later.

In 2020, after another bad fall and nights of confused searching through the house, Alex took her mother to their family doctor, who gave a general diagnosis of dementia. Alex describes it as a diagnosis “which felt like a catastrophic moment.” Determined to keep her mother at home, Alex worked remotely from her mother’s house and cared for her through the pandemic. After what Alex describes as a transient stroke in 2022, Anna struggled with everyday tasks, and her hallucinations grew frightening: she saw thieves coming through the backyard fence. Alex had the fence rebuilt. It did not help. “So I realized that reason wasn’t going to help,” she says.

A doctor at Baycrest later gave a more precise diagnosis: Alzheimer’s disease with Lewy body disease. The hallucinations, the balance problems, the falls and the fear all fit. As Dr. Sim explains, paranoia can have different roots: in Alzheimer’s it often follows misplacing something and suspecting it was taken, while in Lewy body disease people may actually see intruders.

Why does a precise dementia diagnosis matter?

A precise diagnosis helps families understand where symptoms come from, anticipate what may come next and plan care, rather than facing each change as a shock.

For Alex, learning about Lewy body disease helped the pieces fit together. Jay Ingram notes that one of the hardest parts of dementia is not knowing what will happen next; knowing which symptoms tend to appear early and late helps caregivers prepare. Dr. Sekuler adds another benefit: understanding that difficult behaviours come from the disease.

The type also matters for treatment. Lecanemab, the first drug in Canada that targets the underlying biology of Alzheimer’s disease, was approved with conditions by Health Canada in October 2025 for people with mild cognitive impairment or mild dementia due to Alzheimer’s, with confirmed amyloid build-up. As Dr. Sekuler points out, a drug that targets Alzheimer’s does not treat Lewy body or vascular disease, which is one reason mixed dementia is so hard to treat.

The episode’s key actions: follow up with a health-care professional if you notice unexplained changes in behaviour or function, try to get as precise a diagnosis as possible, and use it to anticipate changes and guide treatment.

What does Alex want other caregivers to know?

Recognize when you have reached the limit of what you can manage alone, and ask for help.

Alex had promised her mother she could stay in the home she loved, and for years she tried to do it all while working full time. After Anna disappeared for a few terrifying minutes in a supermarket in 2022, Alex applied for long-term care. Six months later, Baycrest’s Apotex Centre offered a bed. She felt relief, guilt and fear. Within about two months, Anna began to settle. “The move was actually a brilliant move, although I didn’t see that at the time,” Alex says. Today, Anna is 94, and Alex visits her every day. They speak Italian together, which Alex relearned during the pandemic to stay connected, and when Alex shows her mother one of her paintings, Anna’s hand still moves as if holding a brush.

Alex is far from alone. The World Health Organization reports that family members and friends provide much of the world’s dementia care, averaging five hours of care and supervision a day, and that women provide 70% of care hours. Baycrest’s Canadian Caregiver Assessment & Resources Tool (C-CART) offers free, personalized caregiver support and resources.

Do healthy habits lower the risk of all types of dementia?

Likely, yes. Dr. Sim explains that the brain-healthy habits discussed on Defy Dementia support the brain across the different types, not just one.

Sleep is a good example. A 2013 study in mice found that during sleep, the space between brain cells expanded by about 60%, allowing fluid to wash through and clear amyloid beta faster than during waking hours. Regular exercise and keeping blood pressure and cholesterol in check also support the brain. The 2024 Lancet Commission identified 14 modifiable risk factors and estimated that addressing them could prevent or delay up to 45% of dementia cases worldwide.

Dr. Sim’s advice is to choose the strategies that suit you rather than trying to do everything, because the stress of chasing a perfect checklist may do more harm than good. The biggest risk factor for dementia is aging, and everyone is aging.

Frequently asked questions about dementia types

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

Dementia is an umbrella term for symptoms such as memory loss and confused thinking that are caused by brain diseases. Alzheimer’s disease is one of those diseases and the most common, contributing to 60 to 70% of dementia cases worldwide, according to the World Health Organization. All Alzheimer’s is dementia, but not all dementia is Alzheimer’s.

What are the main types of dementia?

The four most common types are Alzheimer’s disease, vascular dementia, Lewy body dementia and frontotemporal dementia. Each is caused by a different disease process, affects different parts of the brain, and tends to cause a different pattern of symptoms. Many people have more than one type at the same time.

What is mixed dementia?

Mixed dementia means a person has more than one dementia-causing disease at once, such as Alzheimer’s disease with vascular disease, or Alzheimer’s with Lewy body disease. Brain studies after death show mixed disease is common in older adults, and having several diseases together makes symptoms more likely to appear.

What are common signs of Lewy body dementia?

Key signs include seeing things that are not there, often people or small animals; acting out dreams during sleep; stiffness, slowness and shuffling like Parkinson’s disease; and thinking that changes from hour to hour or day to day. Falls and drops in blood pressure are also common. A doctor should assess any of these changes.

Why is it important to get a specific dementia diagnosis?

A precise diagnosis helps families understand where symptoms come from, anticipate changes and plan care. It can also help people see that difficult behaviours are caused by the disease, not their loved one. Some newer treatments, such as lecanemab, are approved only for early-stage Alzheimer’s disease, so the type matters.

Can healthy habits lower the risk of all types of dementia?

Likely yes. Neurologist Dr. Valerie Sim explains that habits such as good sleep, regular exercise and managing blood pressure and cholesterol support the brain across the different types of dementia. The 2024 Lancet Commission estimated that addressing 14 modifiable risk factors could prevent or delay up to 45% of dementia cases.

Research referenced

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3. Schneider JA, Arvanitakis Z, Bang W, Bennett DA. Mixed brain pathologies account for most dementia cases in community-dwelling older persons. Neurology. 2007;69(24):2197-2204. doi:10.1212/01.wnl.0000271090.28148.24
4. Kapasi A, DeCarli C, Schneider JA. Impact of multiple pathologies on the threshold for clinically overt dementia. Acta Neuropathologica. 2017;134(2):171-186. doi:10.1007/s00401-017-1717-7
5. Xie L, Kang H, Xu Q, et al. Sleep drives metabolite clearance from the adult brain. Science. 2013;342(6156):373-377. doi:10.1126/science.1241224
6. Livingston G, Huntley J, Liu KY, et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. The Lancet. 2024;404(10452):572-628. doi:10.1016/S0140-6736(24)01296-0
7. Health Canada. Regulatory Decision Summary for Leqembi (lecanemab). Decision October 2025. Drug and Health Products Portal