A study of more than 500 healthy adults suggests that people with a higher genetic risk for Alzheimer's disease experience more nocturnal micro-awakenings, brief episodes of brain activity that fragment sleep without fully rousing the sleeper.
The pattern appeared in adults aged 50 to 69, but not in younger participants aged 18 to 31, according to research from the GIGA Neurosciences laboratory at the University of Liège in Belgium.
The findings were reported on August 11, 2026, in the journal Sleep. They add to a growing body of work exploring whether sleep could serve as a low-cost, non-invasive marker of vulnerability to Alzheimer's decades before memory symptoms appear.
Why the silent phase matters
Alzheimer's disease is now understood as a decades-long process. Abnormal protein deposits, including tau tangles and amyloid plaques, can begin building up in the brain 20 years or more before a person notices any change in memory or thinking.
Also read: Researchers highlight an easy way to improve stability
That long, symptom-free window is called the preclinical or silent phase. It is also the period when researchers believe interventions have the best chance of slowing damage, which is why identifying reliable early markers has become a major focus in dementia research.
An estimated 7.2 million Americans age 65 and older are living with Alzheimer's dementia today, according to the Alzheimer's Association's 2025 Facts and Figures report. That number could reach 13.8 million by 2060 without medical breakthroughs.
What the researchers measured
The Belgian team calculated polygenic risk scores, which combine the effects of many genetic variants into a single estimate of inherited vulnerability, and compared these scores with detailed measures of sleep. In healthy middle-aged adults, a higher polygenic risk score was linked to more frequent micro-awakenings during the night. No such link showed up in the younger group.
Puneet Talwar, a researcher at the GIGA ULiège laboratory, said the pattern is meaningful even if it cannot predict individual risk. "These micro-awakenings are therefore not insignificant, certain profiles could promote the accumulation of proteins involved in Alzheimer's disease and be associated with increased vulnerability," he said.
Also read: How eating bananas every day can affect your blood pressure, gut and mood
The researchers stress that a polygenic risk score cannot tell any one person whether they will develop the disease. The association is statistical and needs to be confirmed in larger and longitudinal studies.
A tiny brain region at the center
Much of the team's interest centers on the locus coeruleus, a brainstem nucleus roughly the size of a grain of rice that helps regulate wakefulness, attention and sleep. It is one of the first brain regions where abnormal tau protein appears, sometimes in early adulthood, well before any cognitive symptoms emerge.
If the locus coeruleus is where the earliest damage takes hold, then subtle disturbances in the sleep processes it controls could plausibly show up long before memory loss. That is the hypothesis the Liège group is now pursuing with high-resolution imaging.
Sleep itself also plays a housekeeping role. During deep sleep, the brain's glymphatic system helps clear waste products, including amyloid beta and tau. Research has shown that fragmented sleep is associated with greater amyloid burden in brain tissue, suggesting a possible two-way street between poor sleep and neurodegeneration.
Also read: Common drug shows promise in early back pain research
What it means in practice
For now, occasional restless nights are not a reason to worry about Alzheimer's. Micro-awakenings are common at every age and can be driven by stress, alcohol, sleep apnea, an uncomfortable bedroom or an unsettled child.
Gilles Vandewalle, co-director of the GIGA CRC In Vivo Imaging platform, said the goal is a practical, accessible tool. "Sleep could become an accessible marker for the early identification of vulnerable individuals," he said.
People who notice persistent sleep problems, loud snoring, gasping during sleep, chronic insomnia or unusual daytime drowsiness should discuss them with a physician. Treating sleep apnea and improving sleep quality are already recommended for general brain and cardiovascular health, regardless of dementia risk.
The Liège team plans further work to see whether specific patterns of nighttime brain activity can be turned into a usable screening signal. If they can, sleep may join blood tests and brain scans in the toolkit doctors use to catch Alzheimer's during its long silent phase.
Also read: Your high blood pressure may have a hormonal cause that most doctors never test for