What is Alzheimer's disease?
Alzheimer's disease is a progressive neurodegenerative disorder characterized by the progressive loss of nerve cells in the brain. Pathologically, it is characterized by two types of deposits:
- Beta-amyloid plaques: Extracellular deposits of a fragment of the amyloid precursor protein. They often form decades before the first clinical symptoms appear.
- Tau fibrils (neurofibrillary tangles): Intracellular deposits of a misfolded protein that normally stabilizes the support structure of nerve cells. Tau pathology correlates more closely in time with clinical symptoms than amyloid does.
The result is progressive cell death, which initially affects the hippocampus (memory) and then spreads extensively to the cerebral cortex. The clinical picture follows this progression: short-term memory first, then orientation, language, executive function, and personality.
→ For an overview of all forms of dementia and how they differ: Dementia in Old Age.
- Germany today: Approximately 1.2 million people with Alzheimer’s (about two-thirds of all dementia cases).
- Prevalence by age: Rare in people under 65 (early-onset Alzheimer’s); after age 65, the incidence roughly doubles every five years.
- Gender ratio: Women are affected slightly more often, partly due to higher life expectancy and partly due to distinct biological factors.
- Familial forms: Less than 1 percent of all cases are monogenic (mutations in the APP, PSEN1, or PSEN2 genes); these typically manifest before the age of 65.
- Genetic risk factors: The apolipoprotein E gene (APOE)—particularly the ε4 variant—significantly increases the risk but is not a causal gene in the strict sense.
Symptoms and Course: The Three Phases
The course of Alzheimer’s disease can be roughly divided into three phases, which may vary in duration from case to case—ranging from a few years to more than fifteen years between the onset of symptoms and death.
Daily life can still be managed largely independently, but changes become noticeable—first to the family, and later to the individuals affected. Symptoms often include those also seen in mild cognitive impairment (MCI):
- Frequent difficulty finding the right words
- Short-term memory lapses—recent experiences are not retained
- Decreased ability to concentrate, especially on new or complex tasks
- Uncertainty in unfamiliar surroundings
- Occasional problems with orientation in time and space
- Tendency toward social withdrawal due to feeling overwhelmed
Independence becomes increasingly limited, and the need for assistance rises noticeably. In this phase, it is also important to distinguish this condition from depression in older adults, as both conditions can manifest as a lack of motivation and social withdrawal:
- Significant memory impairment, including for personal history
- Disorientation in the familiar home
- Difficulties with daily activities (getting dressed, preparing meals, personal hygiene)
- Personality changes, mood swings, and sometimes episodes of aggression
- Sleep-wake cycle disturbances, nighttime wandering
- Isolated behavioral abnormalities (restlessness, fidgeting, repetitive actions)
Complete dependence on care in all areas of life. Complications such as aspiration pneumonia and immobility frequently occur in this stage:
- Extensive loss of speech
- Failure to recognize close family members
- Complete incontinence
- Gait disturbances, later bedridden
- Swallowing difficulties — a common cause of aspiration pneumonia
- Aware but unable to respond meaningfully to the environment
The average survival time after diagnosis is 7 to 10 years, depending on age and comorbidities, with significant individual variation. In most cases, the cause of death is not Alzheimer’s disease itself, but pneumonia or another infection in the terminal stage.
Diagnosis: The Path to a Definitive Diagnosis
Modern Alzheimer’s diagnostics are significantly more precise than they were ten years ago. The process consists of three steps. A comprehensive geriatric assessment often forms the basis:
- Clinical testing: MMSE, MoCA, clock drawing test, DemTect—validated brief tests for quantifying cognitive deficits.
- Imaging: MRI or CT to visualize typical atrophy (particularly of the hippocampus) and to rule out other causes (hemorrhages, tumors, normal-pressure hydrocephalus).
- Biomarkers: Lumbar puncture with measurement of beta-amyloid 1-42, total tau, and phospho-tau. Alternatively, amyloid or tau PET. Blood-based biomarkers (plasma-based p-Tau217) have been validated in studies since 2024 and are entering routine clinical practice.
Today, in specialized centers, biomarker-based diagnosis allows Alzheimer’s disease to be distinguished from other forms of dementia with over 90 percent certainty—a level of precision that was only achievable postmortem ten years ago. The differential diagnosis between dementia and depression also plays an important role.
→ An overview of the complete diagnostic pathway: Dementia Diagnostics—From the Clock Test to Biomarker Analysis.
Treatment: What Helps with Alzheimer’s?
The treatment of Alzheimer’s disease is based on four pillars. None of these is sufficient on its own—it is the combination that makes the difference. The field of geriatrics and geriatric medicine also offers a comprehensive overview.
- Cholinesterase inhibitors: Donepezil, rivastigmine, galantamine. Approved for mild to moderate Alzheimer’s dementia. They typically slow progression by six to twelve months but are not a cure. Most common side effects: nausea, diarrhea, sleep disturbances.
- Memantine: NMDA receptor antagonist. Approved for moderate to severe Alzheimer’s dementia. Often used in combination with a cholinesterase inhibitor.
When prescribing medication for older patients, the issue of polypharmacy in older adults must also be considered—interactions between multiple medications taken simultaneously can complicate treatment. The targeted deprescribing of unnecessary medications is therefore an important component of modern geriatric medicine.
Lecanemab and donanemab are new monoclonal antibodies that specifically break down beta-amyloid in the brain. In regulatory trials (CLARITY-AD, TRAILBLAZER-ALZ 2), they demonstrated a 27 to 35 percent slowdown in clinical progression over 18 months in patients with early-stage Alzheimer’s disease.
Important to note:
- Suitable only for patients with mild cognitive impairment or mild Alzheimer’s dementia
- A prerequisite is biomarker evidence of amyloid pathology
- Contraindications include certain genetic profiles (two copies of the APOE-ε4 variant) and pre-existing conditions such as microbleeds
- Regular MRI follow-ups are mandatory due to the risk of amyloid-related imaging abnormalities (ARIA)—cerebral edema and microbleeds
- Treatment is available only at specialized centers with the appropriate expertise
These therapies are not a miracle cure, but rather a first step in a long therapeutic process. The slowing of disease progression is real, but moderate. A cure remains impossible.
- Cognitive Stimulation Therapy (CST): Structured group programs with effects comparable to those of anti-dementia medications.
- Physical activity: Aerobic exercise and strength training slow progression and improve mood. For older patients, fall prevention is also a key concern.
- Social engagement: Loneliness is an independent risk factor for disease progression.
- Nutrition: The Mediterranean and MIND diets have shown protective effects in cohort studies. Malnutrition in older adults has been shown to negatively impact cognitive decline.
- Correcting hearing and vision impairments: According to the Lancet Commission 2024, uncorrected hearing loss is one of the greatest modifiable risk factors for dementia progression.
- Sleep hygiene: Healthy sleep plays a distinct role in the breakdown of amyloid—a process known as glymphatic clearance.
Concomitant symptoms such as depression, sleep disturbances, agitation, and psychotic symptoms are treated on an individual basis—with particular caution regarding neuroleptics, which increase the risk of mortality in Alzheimer’s patients and should only be used for short periods and at the lowest possible dose. Delirium in older adults can also cause an acute worsening of the condition and requires targeted delirium prevention.
→ For detailed information on the current landscape of dementia treatment: Dementia Treatment 2026.
Living with Alzheimer’s: What Family Members Need to Know
- Early Planning: A power of attorney for healthcare, a living will, and a guardianship directive should be drawn up while the individual still has full legal capacity.
- Care Level: The application to the Medical Service explicitly takes cognitive impairments into account. A care level provides access to services and support.
- Daily Routine: Regular routines, familiar objects, and clear visual cues (clock, calendar) reduce anxiety and restlessness.
- Communication: Short sentences, eye contact, patience. Do not correct unless necessary. “Validation”—acknowledging the emotional content of what is said rather than insisting on reality—is often more effective than sticking strictly to the truth.
- Self-Care and Support: Family caregivers are at increased risk for depression and exhaustion. Day care, short-term care, and support groups are not a sign of weakness but a structural necessity for sustainable care. Early geriatric rehabilitation can help preserve existing abilities for as long as possible.
When should you see a doctor?
The earlier the diagnosis is made, the more options remain. Specific reasons:
- Repeated forgetfulness that noticeably interferes with daily life
- Frequent problems with orientation in familiar surroundings
- Difficulty finding the right words and changes in speech ability
- Personality changes or social withdrawal
- Confusion regarding financial or administrative matters
- Conflicts among family members regarding the assessment of the situation
The first point of contact is the primary care physician, who, if dementia is suspected, will refer the patient to a neurologist, a memory clinic, or a geriatrician. A frailty screening may also be useful for early risk assessment, as frailty syndrome is closely linked to the risk of dementia. The combination of specialized neurological diagnostics and geriatric assessment is particularly valuable for older patients with multiple chronic conditions.
→ How a comprehensive geriatric assessment works: Geriatric Assessment.
