Tiny interruptions during sleep may offer an early clue about a person’s risk of Alzheimer’s disease, according to new research from the University of Liège in Belgium.
The study suggests that frequent brief awakenings may be connected with a higher inherited risk of developing the disease years before memory problems appear.
Alzheimer’s disease is the most common cause of dementia. It slowly damages brain cells and can affect memory, thinking, language, judgment, and the ability to manage everyday life.
Changes in the brain can begin many years before a person receives an Alzheimer’s diagnosis. Scientists are therefore searching for early signs that could identify people at greater risk while they are still healthy.
Sleep has become an important part of that search. People with Alzheimer’s often have disturbed sleep, but researchers are still trying to understand whether unusual sleep begins early enough to serve as a warning sign.
The new study focused on very short awakenings during the night. These micro-awakenings are brief bursts of brain activity that interrupt sleep, even though a person may not become fully awake or remember them the next morning.
Researchers studied sleep in more than 500 healthy adults. They used recordings of brain activity during sleep to count these brief awakenings and then compared the results with each participant’s genetic risk for Alzheimer’s disease.
A genetic risk score combines information from many small differences in a person’s DNA. It does not tell researchers that someone will definitely develop Alzheimer’s, but it can show whether that person has a higher or lower inherited chance of developing the disease.
Among adults in late middle age, whose average age was about 59, more frequent micro-awakenings were linked to a higher genetic risk for Alzheimer’s. Researchers did not find the same clear pattern among younger adults.
The result is interesting because the people in the study were healthy and had not developed the memory and thinking problems normally associated with Alzheimer’s. This raises the possibility that changes in sleep may appear before obvious symptoms.
The researchers are particularly interested in a tiny area of the brainstem called the locus coeruleus. Although it is only about the size of a grain of rice, it helps control alertness, attention, and the movement between sleeping and waking.
This brain area may also be important in Alzheimer’s disease. Abnormal changes involving a protein called tau can appear in the locus coeruleus very early in life, long before widespread damage develops elsewhere in the brain.
Because the locus coeruleus helps regulate sleep, early changes in this area could possibly affect the way a person moves through the different stages of sleep. That could help explain why certain patterns of micro-awakenings are associated with greater inherited Alzheimer’s risk.
The researchers also noted that broken sleep could have wider effects on brain health. Deep, steady sleep supports many important processes, including memory and the normal removal of waste products from the brain.
However, the study does not show that brief awakenings cause Alzheimer’s disease. It also does not prove that people who wake frequently during sleep will eventually develop dementia.
Many common factors can disturb sleep, including stress, noise, pain, sleep apnea, medicines, alcohol, and changes that occur naturally with age. Genetic risk is also only one part of Alzheimer’s disease, which develops through a complicated mix of age, genes, health, and environmental factors.
The research was published in the journal Sleep. Senior researcher Gilles Vandewalle and colleagues said sleep could eventually become an easy-to-measure sign that helps identify people who may be more vulnerable to Alzheimer’s disease.
The study is valuable because it connects detailed sleep measurements with genetic information in people who are still healthy. Its large healthy sample also allows researchers to study changes before dementia has already altered sleep in obvious ways.
Still, the findings should be treated as an early step rather than a new test for Alzheimer’s. The study found an association, not a cause, and the pattern appeared mainly in late-middle-aged adults, so researchers need to confirm it in other groups and follow people for many years.
Future studies will need to determine whether micro-awakenings can predict actual Alzheimer’s disease, rather than simply matching genetic risk. If that link is confirmed, an ordinary night’s sleep could one day provide doctors with useful information about brain health long before serious memory loss begins.
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Source: University of Liège.
