Alzheimer’s disease is the most well-known and widespread dementia, and there is currently no cure for it.
It sees the patient irretrievably lose his memory and his ability to judge, during an evolution that usually takes several years.
At least 30 million people worldwide are affected, according to the World Health Organization (WHO). This figure remains inaccurate because it is not easy to distinguish Alzheimer’s disease from other dementias, such as vascular disease.
Like other dementias, Alzheimer’s disease is one of the major contemporary public health problems as people with dementia lose their independence, placing a heavy emotional burden on their loved ones and financially on health systems.
This is all the more so in the countries where the population is the oldest, and therefore the main developed countries, with the disease occurring widely in those over 65 years of age. It also affects women much more than men.
Compared to other dementias, the disease, first described by the German physician Alois Alzheimer in the early twentieth century, is distinguished by its mode of action, which is twofold.
The first of these two phenomena, which is commonly found in Alzheimer’s patients, is the formation of protein plaques, called amyloids, which compress the neurons and eventually destroy them.
The second comes from another type of protein, called Tau, which is present in neurons. In patients, they form clusters that also end up killing the affected cells.
But it is not yet clear how these two phenomena are related. It is also largely unknown what causes them to appear, and even how they explain the course of the disease. Thus, the long-held hypothesis that the formation of amyloid plaques is a trigger and not the consequence of other mechanisms is increasingly being questioned.
Consequence: Despite decades of research, no treatment is currently available to cure the disease or prevent its onset.
A major breakthrough in 20 years, a treatment by the US laboratory Biogen, which targets amyloid proteins, has had some results and has been approved this year in some cases by US authorities. But its effects remain limited and its therapeutic interest is not unanimous.
Another debate concerns the prevention of the disease, since it 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.
The authors of a 2020 baseline study estimate that 40% of dementias could be prevented and delayed by playing on these symptoms. But this figure is disputed by other researchers who find this reading too simplistic.