Alleging nearly 900,000 people in France, Alzheimer's disease is the most common form of dementia. Still incurable in today, this neurodegenerative disease causes slow, progressive and irreversible dysfunction, then the death of the nerve cells in the brain.
In fact, the brain of a person affected by Alzheimer's disease differs from the brain of the "healthy" brain of the elder who is not affected by the disease. But from when can we see a different evolution between the brain of the diseased person and the brain with normal aging?
This is the subject of a study jointly conducted by researchers from the CNRS, Ecole Pratikue des Hautes Etudes (EPHE) and the University of Valencia (Spain) and published in the journal. Scientific Reports.
Atrophy of the hippocampus 40 years ago
To better understand how and when the brain affected by Alzheimer's disease evolves differently from normal brain aging, the researchers analyzed more than 4000 MRI brain. 2944 MRs are from healthy control, ranging from a few months to 94 years: their analysis enabled them to establish a "normal" model of average brain development.
They then compared this model with an average pathology model, of 1385 people over 55 years of age and affected by Alzheimer's disease and 1 877 younger controls.
This analysis enabled them to highlight the early divergence of pathological models with respect to the normal pathway of aging. Indeed, it seems that two areas of the brain are atrophying even before the onset of the first symptoms of the disease: the hippocampus involved in the process of memory and the amygdala, the center in which emotions are managed. Hypokampus modification was observed 40 years ago in sick patients and about 40 years for amygdala.
In addition, researchers have found that cerebral cavities, called lateral ventricles, are prone to early spread in people with Alzheimer's disease, compared to normal healthy brain subjects. These ventricles participate in the secretion and circulation of cerebrospinal fluid in which the central nervous system is implanted. However, researchers admit, this finding is more limited than atrophy of the hippocampus and amygdala, as seen in older healthy subjects. Their enlargement is therefore associated with brain aging, and not particularly with Alzheimer's disease.
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