For people living with Alzheimer's disease, the pace of decline varies enormously from one patient to the next, and doctors have few reliable ways to predict who will deteriorate quickly. A study published in Neurology suggests that a night in the sleep lab may hold part of the answer, by measuring two things simultaneously: the strength of specific brain waves produced during deep sleep, and the level of a wake-promoting brain chemical called orexin.
Tracking 60 Patients for Three Years
The research, led by Arsenio Paez and Thien Thanh Dang-Vu at Concordia University in collaboration with colleagues in Spain and Sweden, followed 60 adults with mild to moderate Alzheimer's disease — 30 of them women, with an average age of 74.7 — over three years. Using overnight sleep recordings, the team measured two features of non-REM sleep: sleep spindles, brief bursts of brain activity linked to memory consolidation, and slow oscillations, the large, synchronized waves characteristic of the deepest stage of sleep. They also measured orexin levels in participants' cerebrospinal fluid.
Orexin is a neurotransmitter best known for promoting wakefulness and regulating appetite; it is also the target of a newer class of insomnia drugs, called orexin antagonists, that block its activity to help people fall and stay asleep.
Stronger Brain Waves, Slower Decline
Patients who produced stronger, longer, and denser sleep spindles and slow oscillations during deep sleep experienced significantly less cognitive decline over the three-year follow-up than those with weaker signals. Because spindles and slow oscillations are the physiological hallmarks of memory consolidation during sleep, the finding suggests that patients whose brains still perform this process effectively retain more cognitive ground as the disease progresses.
The picture for orexin ran in the opposite direction. Patients with elevated orexin levels were more likely to show poorer memory and thinking, more severe behavioral and psychiatric symptoms, and higher levels of biological markers tied to neurodegeneration and inflammation, including tau proteins associated with Alzheimer's pathology. Elevated orexin also predicted increases in phosphorylated tau and other markers linked to disease severity over the study period.
A Possible New Way to Track — and Treat — the Disease
The findings point toward two related, practical uses. First, sleep spindle and slow oscillation strength could serve as a relatively simple, non-invasive marker for tracking how quickly an individual patient's Alzheimer's disease is likely to progress, something clinicians currently struggle to predict. Second, because orexin-blocking drugs already exist and are approved for insomnia, the study strengthens the case for testing whether lowering orexin activity could slow cognitive decline in Alzheimer's patients directly, rather than simply treating their sleep problems as a side effect of the disease.
"Sleep could become an accessible window into how the disease is unfolding in a given patient," the researchers noted, pointing to the potential for overnight sleep recordings to guide which patients might benefit most from orexin-targeted treatment.
Limitations and Context
The study is observational, meaning it shows an association between sleep physiology, orexin levels, and cognitive outcomes, but cannot prove that boosting sleep spindle activity or lowering orexin directly slows Alzheimer's progression. The sample size of 60 patients, while followed carefully over three years, is modest, and all participants already had diagnosed mild to moderate Alzheimer's disease rather than being followed from a pre-symptomatic stage. Clinical trials would be needed to determine whether orexin antagonists, already on the market for insomnia, actually alter the disease course when used in Alzheimer's patients.
What This Means for Patients
For patients and families navigating an Alzheimer's diagnosis, this research offers a step toward more individualized prognosis: rather than treating all patients as following the same trajectory, sleep recordings measuring spindle strength and orexin levels could eventually help identify who is likely to decline faster and who might benefit most from closer monitoring or early intervention. It also adds weight to ongoing research into whether existing orexin-blocking insomnia medications could be repurposed as a disease-modifying treatment, a question that will require dedicated clinical trials to answer.
The study was published in Neurology (DOI: 10.1212/wnl.0000000000218307).
