What are the causes?
Alzheimer's disease is caused by progressive neuronal degeneration. Short-term memory is affected first as neurons in the hippocampus degenerate, and the disease then gradually spreads to the entire brain.
The degeneration is caused by changes to two molecules:
- amyloid-beta peptide: an abnormal accumulation of amyloid-beta peptide, which occurs naturally in the brain, results in amyloid plaques (also known as senile plaques). This build-up is toxic for nerve cells in Alzheimer's patients;
- tau protein: tau normally helps maintain neuron structure, but in Alzheimer's patients it is altered, disrupting neuron structure and leading in turn to an accumulation of neuronal filaments (neurofibrillary degeneration) and ultimately to nerve cell death.
The degeneration caused by Alzheimer's disease is very gradual and years can pass before symptoms occur.
What are the risk factors?
The main known risk factors are as follows:
- Age is the primary known risk factor for dementia, but dementia is not an inevitable consequence of aging.
- Moreover, dementia does not only affect elderly people, with early onset dementia (when symptoms emerge before the age of 65) representing up to 9% of cases.
- Several genes are thought to be linked to an increased susceptibility to Alzheimer's disease (amyloid peptide metabolism genes, genes involved in inflammation, genes that allow communication between neurons, etc.).
- Conversely, it appears that some genes protect against the disease.
- Alzheimer's disease may be more likely in inactive people, those who have had several anesthetics, or those with untreated cardiovascular risk factors (diabetes, high blood pressure, etc.).
- But environmental factors can have a positive impact on what is known as the "cognitive reserve" – it is thought that the function of lost neurons can be compensated by stimulating the brain, and the onset and/or severity of early symptoms can be delayed by education, a stimulating job or an active social life.
What are the symptoms?
The first symptoms are a loss of independence and a progressive impact on everyday activities such as washing, dressing and getting around. Alzheimer's disease develops over several years.
Other symptoms can emerge at each stage of dementia.
- Mild: part of the brain region responsible for short-term memory is affected; patients suffer from memory lapses, for example losing things, that may seem harmless but worsen over time.
- Moderate: various brain regions are affected; patients progressively lose independence, finding it hard to recognize people they know and struggling with everyday tasks and decision-making.
- Severe: the damage to the brain worsens; patients lose their memory completely and are virtually incapable of carrying out everyday tasks on their own. They may get lost, struggle with basic activities and find it difficult to speak.
How is Alzheimer's disease diagnosed?
Although there is no cure for Alzheimer's disease, it is possible to slow down its progression, especially if diagnosed early. Early diagnosis can also enable patients to make arrangements for the future while they are still able to think clearly and make decisions.
The French National Authority for Health has published a guide containing best practices for diagnosing Alzheimer's disease (in french) aimed at health professionals. It provides details of the different steps in diagnosing the disease (clinical and biological assessment, neuropsychological testing and medical imaging).
People generally go to see their family physician if they are having difficulties in daily life, such as memory lapses, problems coping with certain tasks, disorientation in space and time and mood swings.
The physician begins by asking the patient questions to rule out any other causes of the symptoms. A screening process is then carried out involving neuropsychological tests to assess certain aspects of memory and the completion of simple tasks. Various brain scans can also be performed to confirm the presence of amyloid plaques or atrophy of brain structures such as the hippocampus. For individuals experiencing dementia symptoms, Alzheimer's disease is generally the first possibility explored.
What treatments are available?
Alzheimer's disease is a health and social burden for all countries with an aging population because there is currently no cure.
Four drugs are available on the market: donepezil, rivastigmine, galantamine and memantine. They do not cure Alzheimer's disease but they can slow the progression of the condition or ease behavioral symptoms, for example leading to improvements in thinking, memory, communication and daily activities.
The confusion and disorientation caused by Alzheimer's disease makes it particularly challenging for patients, families and caregivers. Therapy is based on:
- acknowledging the psychological impact of the disease,
- and offering activities that improve everyday life for patients and their relationships with family members and caregivers. These activities may involve:
- art (painting, sculpture, writing, music, theater, etc.);
- exercise (gentle stretching, tai chi, mindfulness or sophrology, relaxation techniques, etc.);
- cognitive therapy (memory training, etc.).
How can Alzheimer's disease be prevented?
A healthy lifestyle is recommended to help prevent Alzheimer's disease.
According to the World Health Organization (WHO), "Studies show that people can reduce their risk of cognitive decline and dementia by being physically active, not smoking, avoiding harmful use of alcohol, controlling their weight, eating a healthy diet, and maintaining healthy blood pressure, cholesterol and blood sugar levels. Additional risk factors include depression, social isolation, low educational attainment, cognitive inactivity and air pollution."
How many people are affected?
According to WHO, 55 million people are thought to have dementia worldwide.
In the absence of curative treatment, this number could increase to 82 million by 2030 and 152 million by 2050. There are nearly 10 million new cases each year. In 2019, the global economic cost of dementia was estimated to be 1.3 trillion US dollars.
In France, around 1.2 million people were estimated to have dementia in 2014 (source: Santé publique France). Approximately 900,000 people in France are currently thought to be living with Alzheimer's disease.