Deep sleep protects the brain from Alzheimer’s

The study included 60 adults with mild to moderate Alzheimer’s disease. The participants spent the night in the sleep laboratory at the University of Lleida in Catalonia, where their brain activity was recorded using polysomnography. The following morning, samples of cerebrospinal fluid were taken to measure the levels of orexin and established biomarkers of neurodegeneration. After that, over the course of three years, the participants regularly underwent cognitive and neuropsychiatric tests; this approach made it possible to track how sleep, brain chemistry, and cognitive decline change together over time.

It turned out that people with elevated orexin levels were more likely to experience memory and cognitive decline, more pronounced behavioral and psychiatric symptoms, as well as higher levels of biomarkers associated with neurodegeneration and inflammation. However, this association was mitigated if the patient developed strong sleep spindles and slow oscillations during sleep — types of brain waves that support and preserve memory and occur during the slow‑wave (NREM) sleep phase. This activity appears to create neural resistance against the destructive effects of excess orexin.

As one of the study’s authors, neurologist Thanh Dang‑Vu, explains, there is a direct link between orexin levels and Alzheimer’s biomarkers. If there is too little orexin, it is narcolepsy; if there is too much, there is increased vulnerability to Alzheimer’s. At the same time, the results also open up therapeutic prospects: drugs that block orexin are already used to treat insomnia and are being considered as a possible therapy for Alzheimer’s. Monitoring sleep, slow oscillations, and orexin levels can help track the progression of the disease and determine which patients will benefit from specialized treatment.

According to Dang-Vu, the study reveals new ways to influence sleep in order to slow the progression of Alzheimer’s disease and paves the way for further research.