Sleep Spindles Linked to Slower Cognitive Decline in Alzheimer’s Study

A three-year study of adults with mild to moderate Alzheimer’s disease found that specific brain-wave patterns during deep, nonrapid eye movement (NREM) sleep were associated with less cognitive decline among people with higher levels of the neurotransmitter orexin.

The international study, led by researchers at Concordia University and based on data collected at the Universitat de Lleida in Catalonia, Spain, included 60 participants. Its findings were published in Neurology in 2026.

Orexin is involved in regulating sleep and appetite. In the study, participants with elevated orexin levels in their cerebrospinal fluid were more likely to experience worsening memory and thinking, more severe behavioral and psychiatric symptoms, and higher levels of biomarkers linked to neurodegeneration and inflammation over the follow-up period.

That relationship was weaker in participants who produced stronger sleep spindles and slow sleep oscillations during NREM sleep. These electrical patterns have been associated with memory-related processes and the preservation of cognitive function. The researchers described the activity as a form of neural resilience against the relationship between higher orexin and poorer cognition and mental health.

To gather the data, participants spent one night in a sleep laboratory, where researchers recorded brain activity using overnight polysomnography. Cerebrospinal-fluid samples were collected the next morning to measure orexin and other Alzheimer’s-related biomarkers. The participants then completed cognitive and neuropsychiatric assessments at regular intervals for three years.

The longitudinal design allowed the researchers to examine how sleep activity, brain chemistry, biomarkers and cognitive performance changed together over time. However, the study was observational in its analysis of these relationships. It showed associations between orexin, sleep-wave activity and disease-related outcomes; it did not establish that stronger sleep spindles prevent Alzheimer’s progression or that altering orexin would improve cognition.

The researchers noted that orexin-blocking drugs are already used to treat insomnia and are being investigated as possible treatments for Alzheimer’s disease. They suggested that measuring orexin levels together with sleep spindles and slow oscillations could eventually help track disease progression or identify patients for specialized treatment. Those potential applications remain areas for further study rather than established clinical uses.

The findings add sleep-brain activity and orexin to the study of how Alzheimer’s disease changes over time, while leaving open whether the observed sleep patterns are a cause of slower decline, a consequence of other disease-related factors, or both.