A recent collaborative study between the Research Centre of the Institut universitaire de gériatrie de Montréal (CRIUGM-CCSMTL) and the Biomedical Research Institute (IRBLleida) of Lleida, Spain, has identified certain sleep characteristics that could predict the evolution of cognitive changes and neurodegeneration in people with mild-to-moderate Alzheimer’s disease.
Sleep is vital for brain health and function and plays an important role in memory consolidation. In particular, it promotes the elimination of amyloid-beta and tau proteins, whose accumulation in the brain is associated with the onset of Alzheimer’s disease.
Recent scientific literature suggests that sleep disorders increase the risk of Alzheimer’s disease. However, less is known about whether or how sleep plays a role in the cognitive decline of people already suffering from Alzheimer’s disease.
In this study, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, Arsenio Paez, a doctoral student at CRIUGM and Concordia University, investigated which aspects of sleep physiology can predict the worsening of Alzheimer’s disease.
In collaboration with Thien Thanh Dang-Vu, laboratory director at CRIUGM and Gerard Piñol Ripoll, director of the Cognition and Behaviour Study group at IRBLleida, he found that the activity of sleep spindles and slow waves plays a major role in predicting the trajectory of the disease in persons with Alzheimer. Slow waves and sleep spindles are two types of brain oscillations found during slow wave sleep, or “deep sleep.” Sleep spindles and slow oscillations play important roles in cognition and sleep stability in the face of external stimuli.
An association with biomarkers and cognitive impairment in Alzheimer’s disease
During their work, the researchers observed that higher sleep spindle and slow wave activity with higher levels of cerebrospinal fluid amyloid beta and clinically important ratios of amyloid beta to tau. They also predicted tau levels and other important biomarkers of brain health in older adults with Alzheimer disease. Moreover, elderly people with Alzheimer’s disease who had higher sleep spindle and slow wave activity also showed less cognitive deterioration over the long term. Sleep spindle and slow wave activities therefore predict the accumulation of proteins responsible for Alzheimer’s disease, as well as the evolution of cognitive performance in people with this disease. They are thus predictive biomarkers of neurodegeneration and cognition in people with Alzheimer’s disease and constitute novel therapeutic targets to slow the progression of Alzherimer disease. Their study adds further evidence for sleep as an important predictor of the neurological evolution of patients already suffering from neurodegenerative disease.
Detecting disease progression in the brain
The study analyzed data from 60 participants with mild to moderate Alzheimer’s disease, collected by partners at the IRBLleida in Spain. Patients’ brain activity was recorded overnight with polysomnography (PSG). The following morning, blood and cerebrospinal fluid samples were collected to detect biomarkers associated with Alzheimer’s disease. Participants’ cognition, neuropsychiatric symptoms, and memory were tested the night before PSG, and then again every 12 months for three years. Arsenio Paez and colleagues then examined the participants’ electroencephelograms (EEG) to study the relationship between sleep spindles, slow oscillations, and amyloid-beta and tau protein, as well as cognition.
Delaying the onset of symptoms
Alzheimer’s disease is often detected after the onset of clinical symptoms, once beta-amyloid and tau levels are already high. However, changes in sleep physiology can precede cognitive symptoms in Alzheimer’s disease sufferers by decades. This study adds important evidence for the role of sleep in the development and progression of Alzherimer disease. Little research had investigated the associations between sleep physiology, disease biomarkers and cognition in people already suffering from Alzheimer’s disease, with most previous research having been conducted in healthy older adults.
The results of this study could therefore be used to develop new therapies targeting sleep oscillations to help Alzheimer’s patients preserve their brain health at an earlier stage. Scientific studies have shown that delaying the appearance of clinical symptoms by 5 years can add up to three years of life to Alzheimer’s patients and reduce the cost of care by up to 40%.
About the study
The article “Sleep spindles and slow oscillations predict cognition and biomarkers of neurodegeneration in mild to moderate Alzheimer’s Disease”, by Arsenio Paez and colleagues, was published on January 29, 2025 in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
Media relations
Journalists wishing to interview the researchers should contact relations.medias.ccsmtl@ssss.gouv.qc.ca.