Alzheimer or Dementia: What Difference? Complete Guide to Understanding

1. Dementia: a syndrome, not a disease

The first thing to understand is that dementia is not a disease in itself, but a syndrome — that is, a set of symptoms that can have multiple causes. The official medical term, preferred today in the scientific literature, is major neurocognitive disorder (according to the DSM-5, the Diagnostic and Statistical Manual of Mental Disorders). But the word “dementia” remains widely used in clinical practice and among the general public.

For a dementia syndrome to be diagnosed, three conditions must be met: a significant cognitive decline compared to the previous level, in at least one area (memory, language, attention, praxis, executive functions, perception); this decline must be severe enough to interfere with daily activities and autonomy; and it must not be better explained by another disorder (depression, delirium, medication effect).

Dementia can affect different cognitive functions depending on the underlying cause and the brain regions affected. The main areas involved are memory (especially episodic memory — memories of lived events), language (finding words, understanding, naming objects), executive functions (planning, organizing, solving problems), praxis (coordinating complex gestures), visuospatial functions (navigating in space), and social cognition (recognizing emotions, understanding social situations).

2. Alzheimer's disease: the most common cause

Alzheimer's disease is a specific neurodegenerative disease, characterized by precise and progressive brain lesions. It accounts for between 60 and 70% of all dementia cases, which explains the frequent confusion between the two terms. However, while every Alzheimer's disease leads to dementia in its advanced stage, not every dementia is Alzheimer's disease.

From a neuropathological perspective, Alzheimer's disease is defined by two types of characteristic lesions, highlighted by Aloïs Alzheimer himself in 1906. These lesions spread according to a relatively predictable anatomical pattern — described by Braak stages — starting with the hippocampus and entorhinal regions (hence the early impairment of episodic memory), and then gradually extending to the entire cortex.

Alzheimer's disease typically progresses through several phases. A silent preclinical phase, which can last 15 to 20 years, during which lesions accumulate without causing noticeable symptoms. A prodromal phase (or MCI — Mild Cognitive Impairment — amnesic), characterized by noticeable episodic memory disorders but without significant impact on autonomy. Then the phase of established dementia, mild, moderate, and then severe, with an increasing impact on daily living activities and autonomy.

3. Other forms of dementia: beyond Alzheimer's

Alzheimer's disease is the most well-known, but other conditions can cause a dementia syndrome, with different cognitive profiles, progressions, and management approaches. Knowing them allows for a better understanding of diagnoses and adapting support.

Vascular dementia (15-20% of cases)

Vascular dementia is caused by brain lesions of vascular origin: cerebral infarctions (Stroke), multiple micro-infarctions (leukoaraiosis), or chronic cerebral perfusion disorders. Unlike Alzheimer's disease, its progression is often stair-stepped — worsening in stages after each new vascular episode — rather than gradual and continuous.

Executive functions and processing speed are often more affected than episodic memory at the onset. Vascular risk factors (hypertension, diabetes, atrial fibrillation) are the main preventive levers. Management largely relies on controlling these cardiovascular risk factors.

Lewy body dementia (10-15% of cases)

Lewy body dementia is characterized by abnormal deposits of alpha-synuclein protein (the "Lewy bodies") in neurons. It presents a distinct clinical profile with significant fluctuations in cognitive performance (sometimes from one day to the next), early and recurrent visual hallucinations, a parkinsonian syndrome (slowness, rigidity, balance disorders), and a particular sensitivity to certain neuroleptics that can be dangerous for these patients.

Dementia associated with Parkinson's disease shares similar mechanisms. These forms require specialized management, particularly due to specific medication risks.

Frontotemporal dementia (5-10% of cases)

Frontotemporal dementia (FTD) is a degeneration of the frontal and temporal lobes of the brain. It typically affects younger people (between 45 and 65 years old) than other dementias. Its profile is characteristic: changes in personality and behavior (disinhibition, apathy, socially inappropriate behaviors) or language disorders (primary progressive aphasia) dominate the clinical picture, while episodic memory is preserved for a long time.

This atypical profile can delay diagnosis, with families often consulting first for psychiatric or relational disorders before the neurological nature is recognized.

4. Mixed forms and reversible dementias

It is common, especially among very elderly people, to find mixed forms combining Alzheimer's lesions and vascular lesions. These mixed forms represent a significant proportion of dementias in old age and sometimes complicate the establishment of a precise etiological diagnosis.

Moreover, some causes of cognitive syndrome are potentially reversible: hypothyroidism, vitamin B12 deficiency, severe depression (depressive pseudo-dementia), normal pressure hydrocephalus, iatrogenic effects of certain medications, infections, electrolyte imbalances. This is why a complete biological and clinical assessment is essential before any diagnosis of neurodegenerative dementia — to avoid missing a treatable cause.

5. How do we distinguish between different dementias?

The differential diagnosis of dementias — that is, distinguishing which form of dementia is involved — is one of the most complex tasks in neurology and geriatrics. It relies on several complementary steps that require specialized expertise and sophisticated diagnostic tools.

The diagnostic evaluation of dementia typically includes a thorough clinical interview (medical history, symptom history, medical and family history), a neuropsychological assessment that objectively characterizes the profile of cognitive impairments (memory, language, attention, executive functions, praxis), a biological assessment (to rule out treatable causes), brain imaging (mainly MRI, sometimes PET scan) allowing visualization of regional atrophies, vascular lesions, or amyloid deposits, and sometimes an analysis of cerebrospinal fluid (Alzheimer's biomarkers: beta-amyloid, tau, phospho-tau) or genetic tests in familial forms.

The role of neuropsychological evaluation

The neuropsychological evaluation is central to the diagnosis of dementias. It not only confirms the existence of cognitive decline and measures its severity but also characterizes the profile of impairments — which significantly guides the etiological diagnosis. An early and predominant impairment of episodic memory (with gradual forgetfulness) is characteristic of Alzheimer's disease. Predominant executive and attentional disorders point towards vascular dementia. Behavioral and language disorders with relatively preserved memory suggest frontotemporal dementia.

This evaluation, conducted by a specialized neuropsychologist, includes a battery of standardized tests systematically exploring all cognitive domains. It often constitutes the key element of the differential diagnosis and allows for monitoring changes over time.

6. Alzheimer's disease and dementia: key differences to remember

For a clear understanding, let’s summarize the essential distinctions between Alzheimer's disease and dementia. These nuances, although seemingly technical, have major practical implications for patients, families, and healthcare professionals.

This distinction also has important implications for medical research and the development of new treatments. Clinical trials are generally specific to a particular etiology, and the biomarkers used for monitoring differ according to the forms of dementia.

7. Alzheimer's disease in detail: symptoms and progression

Since Alzheimer's disease accounts for the majority of dementia cases, it is useful to describe its clinical picture and typical progression more precisely. This knowledge helps families better understand what lies ahead and to adapt their support.

Alzheimer's disease typically progresses in three main stages, with duration varying considerably from person to person (on average 8 to 10 years between diagnosis and death, but with significant variations from 3 to 20 years depending on the age of onset, general condition, and access to care).

It is crucial to understand that this evolution is not linear and that many factors can influence it: cognitive and social stimulation, physical activity, quality of support, management of associated disorders (depression, agitation), medical comorbidities.

8. Support and cognitive stimulation: adapt to the cause

A precise understanding of the etiological diagnosis is not just academic: it has direct implications for support and cognitive stimulation. Each form of dementia requires specific approaches to optimize the effectiveness of non-drug interventions.

In Alzheimer's disease, cognitive stimulation is one of the best-documented non-drug interventions to maintain functional abilities and quality of life. It leverages long-preserved memories (implicit memory, procedural memory, emotional memory) to maintain engagement, pleasure, and self-esteem. The most effective activities are those that are individualized, regular, adapted to the current cognitive level, and that preserve a sense of competence.

In vascular dementias, the focus will be on executive and attentional functions, with exercises in planning, organization, and processing speed. In Lewy body dementias, significant fluctuations must be taken into account and the pace of sessions adapted. In frontotemporal dementias, behavioral disorders will require specific approaches in collaboration with specialized teams.

Coordination of care and personalized follow-up

When several professionals (speech therapist, psychomotor therapist, occupational therapist, nursing assistant) and the family are involved with the same person, the coordination and follow-up of stimulation activities are essential to ensure consistency and adjust approaches. A shared follow-up notebook allows for documenting stimulation sessions, observing the evolution of abilities, and facilitating communication among the various stakeholders.

This coordination is particularly important because the effects of cognitive stimulation are cumulative and require regularity and a coherent progression to be optimal.

9. What families need to know

For the relatives of a person with dementia, understanding the diagnosis is often a painful but necessary step. Several essential points can help families better cope with this ordeal and optimize the support of their loved one.

Families should also know that there are many resources for help and support: family associations (France Alzheimer, Lecma-Vaincre Alzheimer), respite platforms, specialized day care, training for caregivers, psychological support, financial assistance (APA, PCH). These resources are often unknown even though they can significantly improve the quality of life for everyone.

10. When to consult? The importance of early diagnosis

The early diagnosis of dementia — ideally as soon as the MCI (mild cognitive impairment) stage — represents a valuable intervention window. It allows for the implementation of cognitive stimulation strategies and medical management at the time when they are most effective, to anticipate important decisions (advance directives, organization of home care, legal and financial aspects), and to access clinical trials for emerging treatments.

Unfortunately, the diagnosis of dementia is still too often delayed in France. On average, there is an 18-month gap between the first worrying symptoms and obtaining an accurate diagnosis. This diagnostic wandering period is detrimental to patients and their families, who remain in uncertainty and cannot access appropriate care.

Validated cognitive tests often constitute the first step in evaluation. These tools, available online or in consultation, help to objectify initial concerns and motivate a specialized medical consultation. They do not replace a professional neuropsychological assessment, but provide a useful first reference for families hesitant to consult.

11. Current treatments and future prospects

Although there is currently no curative treatment for neurodegenerative dementias, several therapeutic approaches can slow progression, improve symptoms, and preserve quality of life. These treatments vary according to the form of dementia, highlighting the importance of accurate etiological diagnosis.

In Alzheimer's disease, specific drug treatments include cholinesterase inhibitors (donepezil, rivastigmine, galantamine) and memantine. Their effectiveness is modest but real on cognitive functions and autonomy. In 2021, aducanumab (Aduhelm) was approved in the United States as the first treatment directly targeting amyloid plaques, although its effectiveness remains debated. Other anti-amyloid treatments are under development.

Non-drug interventions play a central role: cognitive stimulation, adapted physical activity, maintaining social connections, managing the environment, supporting behavioral disorders. These approaches, well-documented scientifically, often constitute the core of daily care.

12. The Role of Technology in Support

New technologies are gradually transforming the support for people with dementia. Cognitive stimulation applications, connected objects for safety, orientation assistance systems, telemedicine, artificial intelligence for symptom monitoring: these innovations open new perspectives for maintaining autonomy and reassuring families.

However, the use of these technologies must be adapted to the capabilities of each person and evolve with the progression of the disease. The challenge is to offer simple, intuitive, and truly useful tools, without creating frustration or digital exclusion.

13. Prevention and Modifiable Risk Factors

Although age remains the primary risk factor for dementia, many modifiable factors can influence the risk of developing these diseases. The Lancet Commission on dementia prevention, intervention, and care has identified 12 modifiable risk factors responsible for about 40% of the overall risk.

These factors include education level (early cognitive training), hearing loss (sensory stimulation), high blood pressure, obesity, smoking, depression, physical inactivity, diabetes, reduced social contacts, excessive alcohol consumption, head trauma, and air pollution. Addressing these factors, even late in life, can delay or prevent the onset of dementia.

14. The economic and societal impact of dementias

Beyond medical and family aspects, dementias represent a major economic and societal challenge. In France, the total cost of caring for people with dementia is estimated at over 30 billion euros per year, including direct medical costs, medico-social care, and indirect costs related to the loss of productivity of caregivers.

With the aging population, the number of affected individuals is expected to double by 2050, rising from 1.2 million today to over 2 million in France. This demographic change requires a profound adaptation of our health system and public policies.

The challenge lies in the development of specialized care offerings, improvement of early diagnosis, support for family caregivers (who provide 80% of the assistance), adaptation of housing and transportation, training for professionals, and innovation in support. The national plan for neurodegenerative diseases 2014-2019 and its follow-ups aim to structure this collective response.