A genetic predisposition to longer sleep is linked to a 21 percent reduced risk of Alzheimer's disease, according to a study in Frontiers in Dementia.
Researchers developed a polygenic score to evaluate inherited sleeping habits, finding that individuals with the highest genetic likelihood of sleeping longer experienced a lower risk of developing the neurodegenerative condition.
To construct the genetic metric, scientists first examined genetic profiles and sleep measurements from 77,700 participants. Sleep duration in this initial group was tracked using wearable activity devices such as wrist-worn sensors, which capture continuous movement patterns to record sleep and wakefulness objectively across large populations.
The resulting polygenic score was then applied to an independent cohort of 264,700 participants to evaluate long-term cognitive health outcomes. Polygenic scores aggregate the subtle effects of thousands of genetic variants across an individual's genome to calculate hereditary tendencies for specific physical traits or medical conditions.
Over a median follow-up period of 12.5 years, Alzheimer's disease was diagnosed in 1,451 participants in the independent cohort. Analysis showed that participants with the highest genetic predisposition to longer sleep logged an estimated 15 additional minutes of sleep per day compared to individuals with average scores.
That estimated difference of 15 daily minutes corresponded to a 21 percent lower risk of developing Alzheimer's disease over the monitoring period.
Understanding Alzheimer's disease and sleep mechanics
Alzheimer's disease is a progressive neurological disorder that gradually destroys memory, thinking skills, and the ability to carry out daily tasks. It is the leading cause of dementia worldwide, affecting millions of older adults and placing a significant burden on global healthcare systems.
Medical researchers have increasingly investigated the relationship between sleep quality and cognitive decline. Restorative sleep plays a crucial role in brain health by enabling the central nervous system to clear metabolic waste products and toxic proteins that accumulate during waking hours.
The research was published in Frontiers in Dementia, a peer-reviewed scientific journal that focuses on open-access research into neurodegenerative conditions, cognitive impairment, and preventative neurology.
Study limitations and protective factors
The authors of the study emphasized that their findings do not mean that sleeping an extra 15 minutes per day directly prevents dementia on its own.
Researchers noted that the polygenic score explained only about 2 percent of the total variation in sleep duration among participants. Because inherited factors account for only a small fraction of overall sleep patterns, the study authors stated that further research is required to confirm whether sleep plays a direct protective role against brain disease.
The findings contribute to a growing body of research examining biological and lifestyle factors linked to dementia risk. Scientists previously established that hormone replacement therapy is associated with a reduced risk of dementia and Alzheimer's disease in women.
