Alzheimer’s disease, which causes progressive memory loss, affects more than 30 million people worldwide and still has no cure, experts recalled on the eve of World Disease Day.
What is Alzheimer’s?
First described in 1906 by the German doctor Alois Alzheimer, this “neurodegenerative” disease leads to a progressive deterioration of cognitive abilities until the patient loses his autonomy.
Symptoms include repeated forgetfulness, orientation problems, executive function disorders (planning, organizing, organizing time, having abstract thoughts) or language disorders.
According to the World Health Organization (WHO), more than 55 million people worldwide suffer from dementia, of which Alzheimer’s disease is the most common form: it represents 60-70% of dementia cases or more of 30 million people.
The number of people with dementia is expected to triple by 2050 due to rising cases in low- and middle-income countries, according to the WHO.
This explosion is going to increase the heavy social burden of the disease on the families of the sick and the health systems.
Alzheimer’s and dementia are already among the leading causes of disability and dependency among the elderly.
Although Alzheimer’s disease is the most common dementia, its precise causes and mechanisms are still largely unknown.
Two phenomena are consistently found among Alzheimer’s patients. On the one hand, the formation of plaques of so-called amyloid proteins, which compress the neurons and end up destroying them.
On the other hand, a second type of protein, known as Tau, present in neurons, accumulates in patients and also ends up causing the death of affected cells.
But it is not clear how these two phenomena are related. What causes their appearance and even to what extent they explain the disease is also largely unknown.
The long-held assumption that the formation of amyloid plaques is always a trigger of disease and not the consequence of other mechanisms is increasingly questioned.
This is largely a consequence of the difficulties in finding the triggers of this disease: despite decades of research, no treatment currently allows curing or even preventing the onset of the disease.
The main advance for 20 years is a treatment from the American laboratory Biogen that targets amyloid proteins. It obtained some results and was approved for certain cases by the United States authorities, but its effects are limited and its therapeutic interest is disputed.
According to the National Institute for Research in Health and Medicine (Inserm) of France, the main risk factor is age: the possibility of contracting Alzheimer’s increases from the age of 65 and skyrockets following the age of 80.
Cardiovascular risk factors, such as diabetes or hypertension, when not controlled in middle age, are also associated with a higher frequency of the disease, although by what mechanisms is not yet known.
Sedentary lifestyle is another risk factor, as well as microcranial injuries observed in certain athletes, such as boxers.
On the contrary, studying and having a stimulating professional activity, as well as an active social life, seem to delay the appearance of the first symptoms and their severity.
In such cases, the brain benefits from a “cognitive reserve” that allows it to compensate, at least for a time, for the function of lost neurons. This effect would be related to brain plasticity, that is, the brain’s ability to adapt.
