Paris (AFP)

Alzheimer's disease, which is the subject of a global awareness day on Tuesday, is the best known and most widespread dementia, with no treatment currently available that can cure or prevent it.

She sees the patient irremediably lose his memory and his capacity for judgment, during an evolution which generally takes several years.

At least 30 million people have it worldwide, according to the World Health Organization (WHO).

This figure remains imprecise because it is not easy to distinguish Alzheimer's disease from other dementias, for example of vascular origin.

Like other dementias, Alzheimer's disease represents one of the main contemporary public health problems because people with the disease lose their independence, placing a significant emotional burden on their loved ones and financial burden on health systems.

This is all the more the case in countries where the population is the oldest, therefore the main developed countries, the disease being widely declared among those over 65 years of age.

It also affects women much more than men.

Compared to other dementias, the disease, described for the first time by the German doctor Alois Alzheimer at the beginning of the 20th century, is distinguished by its mode of action, which is twofold.

The effects of Alzheimer's AFP / Archives

The first of these two phenomena, which are found systematically in Alzheimer's patients, is the formation of protein plaques, called amyloid, which compress neurons and destroy them in the long term.

The second comes from another type of protein, called Tau, and present in neurons.

In patients, they form clumps which also eventually cause the death of affected cells.

But it is not yet clear how these two phenomena are linked.

It is also largely unknown what causes their appearance.

And, despite decades of research, there is currently no treatment that can cure the disease or prevent its onset.

Main breakthrough for 20 years, a treatment from the American laboratory Biogen, which targets amyloid proteins, has obtained some results and has been approved this year for certain cases by the American authorities.

But its effects remain limited and its therapeutic interest is not unanimous.

Another debate concerns the prevention of the disease, since it very rarely has a hereditary component.

Several risk factors - a dozen - are currently listed for all dementias.

The most common are deafness, low education, smoking, depression and isolation.

A person with Alzheimer's irreparably loses memory and judgment, during an evolution that generally takes several years SEBASTIEN BOZON AFP / Archives

The authors of a benchmark study dating from 2020 estimate that 40% of dementias could therefore be avoided and delayed by playing on these symptoms.

But this figure is disputed by other researchers who consider this reading too simplistic.

© 2021 AFP