What is dementia?
Dementia is an umbrella term for progressive diseases of the brain in which cognitive abilities such as memory, thinking, orientation, language and judgment decline so severely that everyday life can no longer be managed independently. That is the decisive point: the cognitive impairment is so pronounced that it becomes relevant to daily life.
Three distinctions are important:
- Normal age-related forgetfulness: Occasionally forgetting names or appointments, which later come back to mind. No impact on coping with everyday life.
- Mild cognitive impairment (MCI, Mild Cognitive Impairment): Measurable deficits in memory tests, but everyday life can still largely be managed. About one in two develops dementia within five years — the other half does not.
- Delirium: An acute, usually reversible state of confusion — not to be confused with dementia, even though the two can occur together.
→ For the distinction between dementia and acute confusion, we recommend the article on delirium in older people.
→ On the precursor stage MCI and the risks of transition: Mild cognitive impairment (MCI).
How common is dementia?
The figures are striking and point to one of the greatest health-policy challenges of the 21st century:
- Germany today: About 1.8 million people with dementia in old age (German Alzheimer Society).
- New cases per year: Around 440,000 people receive a dementia diagnosis every year.
- Prevalence by age: About 1.5 percent among 65- to 69-year-olds. More than 40 percent among those over 90.
- Worldwide: Around 55 million people with dementia — with a forecast of more than 130 million by 2050 (WHO).
In my daily work, this means specifically: dementia is rarely the reason for admission, but almost always a concomitant finding. In many of our geriatric patients, the cognitive impairment has not been formally diagnosed by the time of admission — it only becomes apparent during the geriatric assessment. And every such late diagnosis is a lost window of opportunity.
The forms of dementia
Dementia is not all the same. The exact form determines the course, therapy and prognosis. In clinical practice, we distinguish five main forms:
The most common form. It begins insidiously, typically with disturbances of short-term memory. Characteristic is the deposition of beta-amyloid plaques and tau fibrils in the brain — changes that today can be detected with biomarkers in the cerebrospinal fluid or on a PET scan.
→ For a detailed account of Alzheimer's disease: Alzheimer's — causes, course, therapy.
Caused by circulatory disturbances in the brain — small strokes, chronic microcirculatory damage, vascular changes in high blood pressure and diabetes. The course is often stepwise rather than uniform. Treating cardiovascular risk factors is at the same time the most important preventive measure here.
Characteristic features are visual hallucinations, strongly fluctuating attention over the course of the day and Parkinson-like movement disorders. Lewy body dementia reacts particularly sensitively to certain medications — especially to classic neuroleptics, which can trigger life-threatening side effects. This underlines the importance of a careful medication review in older patients.
Typically begins earlier than Alzheimer's — often between the ages of 50 and 70. The foreground is occupied not by memory disorders but by personality changes, disinhibited behavior or loss of language. It is often misinterpreted for a long time as depression or a psychiatric illness.
In reality, the forms frequently overlap, especially in very old patients. Pure Alzheimer's dementia from the age of 85 is the exception, not the rule. In addition, there are rare causes such as normal-pressure hydrocephalus, dementia in Parkinson's disease and dementia after head injuries — whose correct identification is crucial, because some of them are treatable. Comprehensive information on geriatrics and the medicine of aging helps to put these complex overlaps into context.
Symptoms and warning signs
The global organization Alzheimer's Disease International has compiled ten early warning signs that relatives, too, can reliably assess:
- Memory gaps that impair everyday life (not just occasional forgetting)
- Difficulties in planning and solving familiar tasks
- Orientation problems in familiar surroundings
- Temporal disorientation — day, month, season become uncertain
- Language problems — words are missing, sentences break off
- Objects are found again in unusual places (glasses in the fridge)
- Impaired judgment, especially in money and safety decisions
- Withdrawal from social activities that used to bring joy — a pattern that can also be observed in depression in old age and that requires careful differentiation
- Changes in mood and personality
- Changes in visual perception (distances, contrasts)
???? A single sign proves nothing at all. A pattern of several signs over several weeks or months is a concrete reason to specifically request a clarification — not to wait.
Diagnosis: how is dementia determined?
Modern dementia diagnostics proceed on three levels:
The basis of every diagnosis is the structured conversation with the patient and relatives. It is supplemented by validated short tests:
- MMSE (Mini-Mental State Examination): 30-point scale. Values below 24 indicate cognitive impairment but are too insensitive for mild forms.
- MoCA (Montreal Cognitive Assessment): More sensitive for mild cognitive deficits and early-onset forms of dementia. Today it is regarded as the gold standard in short screening.
- Clock-drawing test: Simple, quick and surprisingly discriminating as a screening tool.
- DemTect: A test specially developed in Germany with good sensitivity for mild forms.
A supplementary frailty screening can help to better assess the overall picture of the patient, since cognitive impairment frequently goes hand in hand with physical frailty.
Magnetic resonance imaging (MRI) or computed tomography (CT) of the head is standard in order to rule out treatable causes (normal-pressure hydrocephalus, haemorrhages, tumors) and to detect typical patterns of atrophy. In specialized centers, FDG-PET or amyloid PET are used.
For a few years now, there has been a diagnostic revolution: biomarkers in the cerebrospinal fluid (beta-amyloid 1-42, tau, phospho-tau) make it possible to distinguish Alzheimer's disease at an early stage with more than 90 percent certainty. Blood-based biomarkers (plasma-based p-tau217) have been validated with high accuracy in studies since 2024 and are gradually entering clinical routine.
→ In detail on the entire diagnostic pathway: Dementia diagnostics — from the clock-drawing test to biomarker analysis. For the distinction between depression and dementia, we also recommend our article Dementia or depression?
Treatment: what really helps
The question that all relatives ask is: can dementia be cured? The honest answer: no. But the course can be slowed, the symptoms alleviated and the quality of life considerably influenced. The biggest mistake would be to forgo treatment because of this.
The evidence is clear: for most people with dementia, non-drug interventions bring the greatest everyday benefit.
- Physical activity: Aerobic training, strength training, dance — lowers progression and improves mood and sleep. Targeted early geriatric rehabilitation can provide structured support here.
- Cognitive stimulation: Targeted programs (CST, Cognitive Stimulation Therapy) have shown effects in studies comparable to anti-dementia drugs.
- Social participation: Loneliness is an independent risk factor — both for the development and for the progression. At the same time, social withdrawal promotes frailty syndrome.
- Nutrition: The Mediterranean and MIND diets show a protective effect in cohort studies. In existing dementia, attention should also be paid to malnutrition in old age.
- Correcting hearing and vision: According to the Lancet Commission 2024, uncorrected hearing and visual impairments are among the greatest modifiable risk factors.
Two classes of active substances have been available for years:
- Cholinesterase inhibitors (donepezil, rivastigmine, galantamine): For mild to moderate Alzheimer's dementia. They do not cure, but typically slow the progression by six to twelve months.
- Memantine (NMDA antagonist): For moderate to severe Alzheimer's dementia. Often in combination with cholinesterase inhibitors.
Since 2024/2025, the landscape has expanded: lecanemab is approved in the USA and the first European countries for early Alzheimer's dementia. It is an anti-amyloid antibody that, in the CLARITY-AD study, showed a slowing of the clinical course by 27 percent over 18 months. Donanemab follows this mechanism of action. These therapies are not suitable for all patients — the prerequisites are an early phase of the disease, biomarker-confirmed evidence of amyloid pathology, close MRI monitoring and the willingness to undergo regular infusions. The topic of polypharmacy in old age must also always be taken into account when deciding on new therapies.
For other forms of dementia — vascular dementia, Lewy body dementia, frontotemporal dementia — there is no specific approved drug therapy; treatment here is symptom-oriented and individual.
→ Our article Dementia therapy 2026 provides an in-depth overview of the current therapy options.
Living with dementia: what relatives need to know
Dementia never affects just one person, but the whole family. The most important recommendations for action for relatives:
- Arrange provisions early: A lasting power of attorney, advance directive and care directive should ideally be drawn up before the diagnosis or immediately afterward, while the patient is still legally competent.
- Apply for a care level: A care level secures financial and organisational support. The classification is carried out by the Medical Service and explicitly takes cognitive impairments into account as well.
- Adapt the living environment: Clear structures, familiar objects, safety measures on the stove and doors, orientation aids (clock, calendar). Targeted fall prevention in the home environment is particularly important here.
- Provide a daily structure: Regular daily routines, sufficient daylight, activity and rest in alternation. Chaos is particularly stressful for people with dementia.
- Rules of communication: Short sentences, eye contact, allowing time. Do not correct where it is not necessary. A validating rather than a confrontational attitude.
- Acknowledge your own limits: Caring relatives have a markedly increased risk of depression in old age. Self-help groups, day care and respite services are not a weakness but a prerequisite for sustainable care. Palliative care support, too, can significantly relieve relatives in advanced stages.
→ For dealing with specific dementia situations: care in dementia and behavioral abnormalities.
When should you see a geriatrician?
The following constellations are clear occasions for a geriatric clarification — alongside or in addition to general practitioner care:
- Several early signs from the list above over weeks or months
- Unclear memory disorder together with many medications — some symptoms are drug-induced and reversible; a targeted deprescribing helps here
- Risk of falling combined with cognitive change
- Confusion after a hospital stay that does not fully subside
- Relatives are increasingly overburdened and are looking for a structured plan
- An operation is imminent — a preoperative geriatric assessment helps to realistically assess the surgical risk in old age
Geriatrics complements general practitioner care and neurology with a holistic view: not only of the cognitive diagnosis, but of the overall situation — medications, mobility, mood, nutrition, social situation. That is the clinical added value — and it is the reason why the geriatric assessment is worthwhile in every dementia clarification.
→ How a geriatric assessment specifically proceeds is described in our article on the geriatric assessment.
Frequently asked questions
Is dementia the same as Alzheimer's?
No. Dementia is an umbrella term for various diseases of the brain that impair cognitive functions. Alzheimer's disease, at 60 to 70 percent, is the most common form of dementia, but not the only one. Alongside it there are vascular dementia, Lewy body dementia, frontotemporal dementia as well as mixed and rare forms.
From what age can dementia occur?
Dementia occurs predominantly in people over 65 years of age. Before the age of 65, one speaks of early-onset dementia (early-onset dementia, FTD). Frontotemporal dementia in particular often begins between the ages of 50 and 70. After the age of 85, the prevalence is more than one third.
Can dementia be prevented?
Not completely, but the risk can be considerably reduced. The Lancet Commission 2024 identifies 14 modifiable risk factors that together explain about 45 percent of the dementia risk — including high blood pressure, diabetes, smoking, lack of exercise, social isolation, uncorrected hearing loss, depressive symptoms and insufficient education in early life. Prevention is possible and effective; the earlier one starts, the better.
Are new drugs such as lecanemab suitable for all forms of dementia?
No. Lecanemab and donanemab are approved exclusively for early forms of Alzheimer's disease and only make sense if an amyloid pathology has been confirmed by biomarkers. For vascular, Lewy body or frontotemporal dementia, this therapy option does not exist. Before every decision, a careful risk-benefit assessment in specialized centers is required — also because of possible side effects such as cerebral edema or microhaemorrhages (ARIA).
What is the difference between dementia and delirium?
The temporal course is the most important difference. Dementia develops over months to years and is usually not reversible. A delirium arises within hours to days, fluctuates over the course of the day and is treatable in most cases — provided the cause is identified. Both can occur together: a delirium in existing dementia is a frequent combination and requires both perspectives.
Is forgetfulness in old age always a sign of beginning dementia?
No. Occasionally forgetting names, appointments or words is part of normal aging. The decisive difference: with normal age-related forgetfulness, everyday life is not substantially impaired, information becomes retrievable again with cues, and the abilities are stable over a longer period. If several of the ten early warning signs occur simultaneously and progressively, a structured clarification is worthwhile — if appropriate also with the help of a screening to differentiate dementia and depression.
