Dementia

Dementia — scientific infographic poster

Table of Contents

  1. What is Dementia?
  2. Dementia, Normal Ageing and Mild Cognitive Impairment
  3. Types of Dementia
  4. Common Symptoms of Dementia
  5. Causes and Risk Factors
  6. Diagnosis
  7. Reversible Causes: Always Rule These Out First
  8. Treatment Options
  9. Supplements and Diet: Honest Evidence Tiers
  10. Prevention Strategies
  11. Living With It: Practical Help for Families
  12. Complications of Dementia
  13. Research Papers
  14. Connections
  15. Featured Videos

What is Dementia?

Dementia is a general term for a decline in cognitive function severe enough to interfere with daily life. It affects memory, thinking, communication, and the ability to perform everyday activities. Dementia is not a single disease but a syndrome with various underlying causes.

A syndrome, not a diagnosis

The word works like "fever" — it describes a state, not a cause. Two things must be true for it to apply: cognition has declined from that person's own previous level in more than one domain, and the decline is now interfering with everyday independence. The second half is what separates dementia from worrying about your keys.

An analogy that families find useful: think of the brain as a large organisation. Memory is the filing system, language is the communications department, executive function is the manager who plans and prioritises, and visuospatial processing is the department that reads maps. Different diseases attack different departments first. Alzheimer's typically takes out the filing system before anything else. Frontotemporal dementia removes the manager while the files stay intact. Lewy body disease disrupts the department that interprets what the eyes are seeing. Knowing which department is failing tells you the likely diagnosis, and more importantly tells the family what help is actually needed.

Because the underlying diseases differ, so do their treatments, their trajectories, and their dangers. Getting the type right is not academic — giving the wrong drug in Lewy body dementia, for instance, can cause severe harm.

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Dementia, Normal Ageing and Mild Cognitive Impairment

This is the question most people arrive with, so here is the practical distinction.

Normal ageing slows retrieval. You forget a name and it surfaces twenty minutes later. You misplace your glasses and then retrace your steps and find them. You forget why you walked into a room, then remember. Crucially, you are aware of the lapses, they annoy you, and nothing in your daily life has changed.

Dementia loses the information rather than delaying it. The conversation from yesterday is not retrieved late — it never registers as having happened. Repeated questions within a single conversation, difficulty following a familiar recipe, getting lost on a route driven for years, trouble managing money that used to be easy, and, tellingly, reduced awareness of the problem itself are the changes that matter. Families usually notice before the person does, and often notice function rather than memory: bills going unpaid, a normally sociable person withdrawing, driving becoming alarming.

Mild cognitive impairment (MCI) sits in between: measurable decline on testing, but everyday independence preserved. It is worth naming because the outlook is genuinely uncertain and is often over-stated in both directions. A proportion of people with MCI progress to dementia, a proportion stay stable, and a proportion return to normal — often because a treatable contributor such as depression, sleep apnea, thyroid disease, B12 deficiency or a medication was found and fixed. MCI is therefore the point at which chasing reversible causes has the highest return.

A simple rule for when to seek assessment: when the change is affecting function, or when the people around you have noticed. Not when you forget a name.

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Types of Dementia

1. Alzheimer's Disease

2. Vascular Dementia

3. Lewy Body Dementia

4. Frontotemporal Dementia (FTD)

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Common Symptoms of Dementia

Symptoms vary depending on the type of dementia but often include:

The early signs that are not about memory

Because "dementia" is filed under memory in most people's minds, the earliest signs are frequently missed. Watch for:

A note on why symptoms swing. Almost everyone with dementia is worse in the late afternoon and evening (often called sundowning), worse when tired, worse in unfamiliar surroundings, and dramatically worse during any physical illness. A sudden change over hours or a day or two is not the dementia progressing — it is delirium, usually from infection, dehydration, constipation, pain or a new medication, and it needs medical attention. Treating the cause usually restores the previous level.

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Causes and Risk Factors

The Lancet standing Commission's 2024 report gathers these into a life-course framework, grouping modifiable risk factors by the stage of life at which they matter most — education in early life; hearing, head injury, blood pressure, alcohol, obesity, smoking, depression, physical inactivity, diabetes and cholesterol in midlife; social isolation, air pollution and vision loss in later life [1]. The practical message is that the highest-leverage window is midlife, decades before any symptom appears.

On genetics. Most dementia is not directly inherited. The APOE4 variant raises risk but is neither necessary nor sufficient — plenty of people carrying it never develop dementia, and most people with Alzheimer's do not carry two copies. Truly inherited, single-gene forms are rare and usually cause disease before 65, often with several affected relatives at similar young ages. Direct-to-consumer APOE testing frequently causes distress out of proportion to what the result can tell an individual.

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Diagnosis

The most valuable part of the assessment is the informant history

Someone who knows the person well should attend and should be able to speak to the clinician, ideally including some time separately. Insight is often impaired, so the account given by the person alone can be reassuring and wrong. Before the appointment, write down: when the first change was noticed and what it was; whether the decline has been gradual or stepwise; specific examples rather than adjectives ("stopped being able to use the washing machine in March", not "confused"); a full medication list including over-the-counter drugs and supplements; alcohol intake; and any family history.

What the cognitive tests do and do not tell you

Brief screening instruments — MMSE, MoCA, Mini-Cog — are useful for tracking change over time and for flagging a problem. They are not diagnostic on their own. A highly educated person can score well while having declined substantially from their own baseline, and someone with limited education, poor English, hearing loss or depression can score badly with no dementia at all. A formal neuropsychological assessment is far more informative when the picture is unclear or the person is young.

Imaging and newer tests

A structural scan (CT or preferably MRI) looks for stroke damage, tumours, bleeding and hydrocephalus, and shows the pattern of shrinkage. FDG-PET can distinguish types by the pattern of reduced brain metabolism. Amyloid PET and cerebrospinal fluid amyloid and tau measurements can confirm Alzheimer's biology, and blood-based biomarkers (notably phosphorylated tau) are moving rapidly into use. Two cautions: these tests confirm the biology, not the syndrome — a positive amyloid result in someone with normal cognition is not a diagnosis of dementia; and access, cost and interpretation vary widely.

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Reversible Causes: Always Rule These Out First

A minority of people presenting with cognitive decline have something treatable. Missing it is one of the more consequential errors in this area, and the tests are cheap. Every workup should cover:

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Treatment Options

How much do the cholinesterase inhibitors actually do?

A Cochrane review of 30 studies in 8,257 participants found donepezil produces small but consistent benefits in cognition, daily function and clinician-rated global state compared with placebo, on moderate-quality evidence [4]. "Small but real" is the honest description. It does not stop the disease, and gains are measured in months of function rather than years.

Practical points: nausea, diarrhoea, vivid dreams and a slow pulse are the common side effects, and taking the tablet in the morning rather than at bedtime often fixes the dreams. Rivastigmine comes as a skin patch, which suits people who cannot swallow tablets. Cholinesterase inhibitors are particularly useful in Lewy body dementia, where they often help the hallucinations and fluctuating attention noticeably more than they help in Alzheimer's. They have no established role in frontotemporal dementia and may worsen behaviour there.

The anti-amyloid antibodies: what the numbers mean

Lecanemab is the first treatment shown to slow decline rather than only mask symptoms, and its results deserve to be reported precisely. In the Clarity AD trial, 1,795 people with early Alzheimer's were randomized to lecanemab or placebo. At 18 months, the change on the CDR-SB scale was 1.21 with lecanemab versus 1.66 with placebo — a difference of 0.45 points on an 18-point scale. Brain amyloid fell substantially. Infusion reactions occurred in 26.4%, and amyloid-related imaging abnormalities with brain swelling or effusions in 12.6% [2].

Read plainly: this is a real, statistically robust slowing of decline, and it is modest — experts genuinely disagree about whether a 0.45-point difference is noticeable to a family. It requires fortnightly infusions, repeated MRI monitoring, applies only to early disease with confirmed amyloid, and carries a meaningful risk of brain swelling or small bleeds. It is not a cure and it does not reverse anything. Anyone considering it deserves those numbers rather than the headline.

Treating behaviour without reaching for a sedative

Agitation, aggression and distress are usually communication. The first question is always what the behaviour is for: pain that cannot be described, constipation, a full bladder, an infection, too much noise, being cold, boredom, or fear of an unfamiliar person. Solving that resolves most episodes.

Antipsychotic drugs carry a documented increase in stroke and death in people with dementia, which is why they carry regulatory warnings and are reserved for severe distress or risk of harm, at the lowest dose, for the shortest time, with a planned review date. If a relative is started on one, ask when it will be stopped — the commonest failure is that nobody ever revisits it. And remember the Lewy body caution above.

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Supplements and Diet: Honest Evidence Tiers

This is a market that preys on fear, so each item is labelled with what the trials actually found.

Ginkgo biloba — tested properly, and it does not work

The GEM study followed 3,069 older adults for a median of about six years on ginkgo 120 mg twice daily or placebo. Dementia developed in 277 on ginkgo and 246 on placebo — a hazard ratio of 1.12 (95% CI 0.94–1.33), that is, no benefit and if anything a numerically higher rate. It also failed to slow progression in those who already had mild cognitive impairment [5]. This is a well-conducted, adequately sized, long trial with a clear negative answer.

B vitamins and homocysteine — promising in a specific subgroup, not established

The VITACOG trial gave B vitamins (folic acid, B6, B12) or placebo to people with mild cognitive impairment. The rate of brain shrinkage over two years was 0.76% per year on treatment versus 1.08% on placebo, and the effect was concentrated in those with raised homocysteine at baseline — where atrophy was 53% lower on treatment [6]. That is a striking result on a brain-imaging outcome in a small trial, and it has not translated into demonstrated prevention of dementia. The reasonable reading: if you have mild cognitive impairment, it is worth having B12, folate and homocysteine measured and any deficiency corrected. That is different from everyone taking B vitamins as insurance.

Vitamin E, omega-3 and the rest

Vitamin E has not prevented dementia in prevention trials, and high doses carry their own risks. Omega-3 supplements have not prevented cognitive decline in the large prevention trials, though eating oily fish is associated with lower risk in observational studies — a distinction worth holding on to. Coconut oil, "brain-boosting" nootropic blends and most branded memory supplements have no meaningful trial support. Where a genuine deficiency exists, correcting it matters; taking supplements to prevent dementia in a well-nourished person is not supported.

Food, plainly

The best-supported eating patterns here are Mediterranean-style and the closely related MIND pattern, and their evidence is largely observational, with mixed trial results. What both amount to in practice: leafy greens most days; berries; vegetables at most meals; legumes such as lentils and black beans; nuts; oily fish twice a week; extra-virgin olive oil as the main added fat; whole grains rather than refined — oats, barley and brown rice; and much less ultra-processed food, fried food and sugary drink. It is worth doing on cardiovascular grounds alone, which is not a small thing given how much dementia is vascular.

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Prevention Strategies

What the trials found — including where the headlines overstated it

Blood pressure — the strongest lever, with an honest caveat. SPRINT MIND randomized 9,361 adults with hypertension to a systolic target below 120 or below 140. Probable dementia occurred in 7.2 versus 8.6 cases per 1,000 person-years — a hazard ratio of 0.83 that did not reach statistical significance. But mild cognitive impairment was significantly reduced (HR 0.81), as was the combined outcome of MCI or dementia (HR 0.85). The trial stopped early for cardiovascular benefit and had fewer dementia cases than expected, so it was likely underpowered for dementia specifically [7]. Fair summary: intensive blood-pressure control clearly reduces cognitive impairment and probably reduces dementia. See Hypertension.

Multidomain lifestyle programmes — real but small. The FINGER trial randomized 1,260 at-risk older Finns to a two-year programme of diet, exercise, cognitive training and vascular risk monitoring, or control. The intervention group did better, with a between-group difference in cognitive score change of 0.022 per year — statistically significant, and small [8]. It is genuine evidence that lifestyle change moves cognition, and it is not a dramatic effect.

Hearing aids — where the headline was wrong. The ACHIEVE trial randomized 977 older adults with hearing loss to hearing intervention or health education. Over three years, the primary analysis found no difference in cognitive decline between groups. A prespecified sensitivity analysis did find a difference between the two sub-cohorts: those recruited from an existing study who were older and at higher risk appeared to benefit, while the healthier volunteers did not [9]. So the honest position is that hearing aids may help people at higher risk, and the widely reported "48% reduction" figure came from that subgroup rather than the trial's main result. Treat hearing loss because hearing matters, and because it plausibly helps — not because prevention is proven.

The rest, briefly: regular physical activity has the most consistent observational support of any single behaviour; social engagement and education build what is often called cognitive reserve; commercial "brain training" games reliably improve your score at that game and do not generalise to everyday function; treating depression, correcting hearing and vision, avoiding head injury, and stopping smoking all belong on the list.

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Living With It: Practical Help for Families

Most of what determines quality of life in dementia is not prescribed.

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Complications of Dementia

Two practical additions. Delirium — a sudden confusional state on top of the dementia — is extremely common during any illness or hospital admission, is frequently mistaken for sudden deterioration, and is largely reversible when its cause is treated. Suspect it whenever the change happened over hours or days rather than months.

And on eating in advanced dementia: swallowing difficulty is part of the late disease. The evidence does not support feeding tubes improving survival, comfort or pneumonia risk in advanced dementia, and careful hand-feeding of favourite foods, at the person's own pace, is generally the kinder and better-supported approach. That is a conversation worth having before a crisis forces it.

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Research Papers

Historical Background

Dementia has been recognized since ancient times, but the modern understanding began with Alois Alzheimer, who in 1906 described the first case of the disease that now bears his name after examining the brain of Auguste Deter. The term "dementia" itself derives from the Latin "de" (out of) and "mens" (mind), and was used in medical literature as early as the 18th century by Philippe Pinel.

Key Research Papers

This list was rebuilt in full after an audit found that ten of the twelve DOI links previously shown here resolved to the wrong paper or to nothing at all. Every citation below was verified live against its own PubMed record — authors, journal, year and title all checked against the source.

  1. Livingston G, Huntley J, Liu KY, et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. Lancet. 2024;404(10452):572-628. PMID 39096926. doi:10.1016/S0140-6736(24)01296-0
  2. van Dyck CH, Swanson CJ, Aisen P, et al. Lecanemab in Early Alzheimer's Disease. N Engl J Med. 2023;388(1):9-21. PMID 36449413. doi:10.1056/NEJMoa2212948
  3. McKeith IG, Boeve BF, Dickson DW, et al. Diagnosis and management of dementia with Lewy bodies: Fourth consensus report of the DLB Consortium. Neurology. 2017;89(1):88-100. PMID 28592453. doi:10.1212/WNL.0000000000004058
  4. Birks JS, Harvey RJ. Donepezil for dementia due to Alzheimer's disease. Cochrane Database Syst Rev. 2018;6(6):CD001190. PMID 29923184. doi:10.1002/14651858.CD001190.pub3
  5. DeKosky ST, Williamson JD, Fitzpatrick AL, et al. Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA. 2008;300(19):2253-62. PMID 19017911. doi:10.1001/jama.2008.683
  6. Smith AD, Smith SM, de Jager CA, et al. Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial. PLoS One. 2010;5(9):e12244. PMID 20838622. doi:10.1371/journal.pone.0012244
  7. Williamson JD, Pajewski NM, Auchus AP, et al. Effect of Intensive vs Standard Blood Pressure Control on Probable Dementia: A Randomized Clinical Trial. JAMA. 2019;321(6):553-561. PMID 30688979. doi:10.1001/jama.2018.21442
  8. Ngandu T, Lehtisalo J, Solomon A, et al. A 2 year multidomain intervention of diet, exercise, cognitive training, and vascular risk monitoring versus control to prevent cognitive decline in at-risk elderly people (FINGER): a randomised controlled trial. Lancet. 2015;385(9984):2255-63. PMID 25771249. doi:10.1016/S0140-6736(15)60461-5
  9. Lin FR, Pike JR, Albert MS, et al. Hearing intervention versus health education control to reduce cognitive decline in older adults with hearing loss in the USA (ACHIEVE): a multicentre, randomised controlled trial. Lancet. 2023;402(10404):786-797. PMID 37478886. doi:10.1016/S0140-6736(23)01406-X

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Connections

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