Subtle shifts in sleep patterns, characterized by an increase in brief awakenings known as micro-awakenings, may serve as an early indicator of an elevated risk for developing dementia, according to a European study.
Micro-awakenings are short periods, typically lasting only a few seconds, during which the brain partially wakes up. These are a normal part of a healthy sleep cycle, and individuals usually experience dozens each night without remembering them. However, the new research indicates that a higher frequency of these micro-awakenings could signal a greater risk of cognitive decline.
The study, which followed 500 adults for up to seven years, found that middle-aged participants who experienced more micro-awakenings were also more likely to possess genetic markers associated with an increased risk of Alzheimer's disease. This includes the APOE4 gene, which has been linked to a 60 percent higher likelihood of an Alzheimer's diagnosis by age 85.
"These micro awakenings are therefore not insignificant," said Dr. Puneet Talwar, a sleep researcher at the University of Liege, Belgium, and co-author of the study. "Certain profiles could promote the accumulation of proteins involved in Alzheimer's disease and be associated with increased vulnerability."
Globally, millions are living with Alzheimer's, and estimates suggest this number is expected to rise significantly in the coming decades. Previous research has also highlighted a potential link between sleep disruption, poor sleep quality, and daytime sleepiness with an increased risk of Alzheimer's disease, possibly due to the buildup of harmful proteins in the brain.
The researchers suggest their findings may offer a method for detecting Alzheimer's risk years before symptoms manifest. Typically, Alzheimer's is diagnosed in individuals aged 65 or older.
The study, published in the journal Sleep, analyzed data from 453 younger adults (average age 22) and 87 middle-aged adults (average age 59). Younger participants slept an average of seven hours and 30 minutes per night, experiencing around 250 micro-awakenings, while middle-aged participants slept for about six hours and 30 minutes, with approximately 180 micro-awakenings.
Upon analyzing the data, researchers found a correlation between a higher number of nightly micro-awakenings and the presence of genes that elevate Alzheimer's risk. The study also utilized brain scans to examine the locus coeruleus, a region in the brainstem that regulates the sleep-wake cycle. The researchers determined that sleep quality, including the ability to fall asleep and sleep depth, depends on the proper functioning of this area. The locus coeruleus is also significant for rapid-eye movement (REM) sleep, crucial for dreaming and memory consolidation, and has been identified in prior research as one of the first brain regions where abnormal protein deposits associated with Alzheimer's appear.
"Sleep could become an accessible marker for the early identification of vulnerable individuals," stated Gilles Vandewalle, a sleep researcher and co-author. Lucie Leroux, head of French-speaking activities at the Stop Alzheimer’s Foundation, which supported the research, added, "This research shows that sleep is not only an indicator of health, but also a potential lever for intervention."