Researchers claim to have discovered a link between Alzheimer's disease and sleep apnea syndrome in the brain tissue of several people: the latter thus confirm the long-suspected links between these two conditions after having observed identical signs of brain damage .

 Decades before the symptoms of Alzheimer's disease are detected, molecular changes occur in the brain. Indeed, two phenomena are well described: the accumulation of beta-amyloid peptides and the transformation of Tau, a structural protein, into abnormally aggregated forms. Together, they progressively promote neuronal degeneration, the loss of memory and executive functions, as Inserm explains. So, while the exact cause of Alzheimer's disease remains a mystery, amyloid plaques toxic to brain cells are known indicators of the disease.

Several studies have shown a correlation between poor quality sleep and the accumulation of this Tau protein in the brain, responsible for the destruction of neurons in Alzheimer's disease. A new study by researchers at the Royal Melbourne Institute of Technology published in the journal Sleep this time shows that toxic amyloid plaques appear in the same place and spread in the same way in the brains of people with obstructive apnea sleep, as in those with Alzheimer's. Until now, scientists knew that these two conditions were related, but the association remained poorly understood.

Sleep apnea: a source of dementia and vice versa

Sleep apnea syndrome (also called obstructive sleep apnea-hypopnea syndrome or OSAHS) is characterized by multiple stops in breathing followed by loud snoring and accompanied by headaches upon awakening. On this subject, the Alzheimer Foundation also specifies "that in addition to its already known effects such as mood disorders and fatigue, sleep apnea represents a risk factor for vascular dementia (arterial hypertension, stroke) and promote the development of Alzheimer's disease. "Inserm specifies that the incidence of the syndrome increases with age: 30.5% of people over 65 are affected.

"If you have sleep apnea in your 40s, you are more likely to develop Alzheimer's disease as you get older, and if you have Alzheimer's, you are more likely to have sleep apnea. than other people your age. », Explains Professor Stephen Robinson, lead author of the study. “Our study is the first to find Alzheimer's-like amyloid plaques in the brains of people with this syndrome. It's a breakthrough in our understanding of the link between these conditions, it opens up new directions for researchers working to develop therapies to treat and prevent Alzheimer's disease. "

Amyloid plaques in people with sleep apnea

The researchers state that significantly, the severity of sleep apnea was linked to a corresponding build-up of amyloid plaques. To come to this conclusion, they autopsied the hippocampus (part of the brain involved in memory processing) of 34 people and the brainstems of 24 people with sleep apnea syndrome. Their goal: to look for the presence of amyloid plaques and neurofibrillary tangles, another indicator of Alzheimer's disease. Because in it, they first appear in a neighboring cerebral area and then move in the hippocampus before spreading to the rest of the cortex.

This analysis allowed them to know how and where these abnormal amyloid clusters aggregated before the patients died. Researchers found both amyloid plaques and neurofibrillary tangles in the brains of people with sleep apnea, but these were the first to be more strongly associated with sleep apnea. sleep. “In the case of mild sleep apnea, we could only find amyloid plaques and neurofibrillary degeneration only in the cerebral cortex near the hippocampus, exactly where they are present at the start of the disease. Alzheimer's disease. ", Note the scientists.

“The next step in our research will be to continue to analyze these samples to gain a full understanding of neuropathology, including signs of inflammation and changes in the blood vessels that supply nutrients to the brain. », They indicate. As the sample size for this research is limited, it will also be necessary to conduct a study with a larger panel of people from different countries to collect more data. But studies like this, using postmortem brain tissue, are only possible if people are willing to donate their brains, healthy or sick, to science.