Nocturnal micro-awakenings linked to genetic risk of Alzheimer's disease

What if certain signs of the disease were to manifest themselves subtly during sleep, long before the first memory problems appear? This is the line of inquiry being explored by a team of researchers at ULiège, with the support of the Stop Alzheimer's Foundation.

A team of scientists from the University of Liège (GIGA Neurosciences), supported by the Stop Alzheimer's Foundation, has analysed the sleep patterns of more than 500 healthy people. Among middle-aged participants, a higher frequency of nocturnal micro-awakenings was found to be associated with a greater genetic risk of developing Alzheimer's disease, whereas this link was not observed in young adults. This research, published in the journal Sleep, suggests that the study of sleep could, in the long term, contribute to the early identification of vulnerable individuals.

For several years, scientists around the world have been investigating the link between sleep disorders and neurodegenerative diseases. A recent study conducted by scientists at the University of Liège offers a new perspective by suggesting that this link may establish itself before any clinical symptoms of the disease appear... To establish this, the researchers exploited the partly genetic nature of the disease (Alzheimer's disease is neither purely hereditary nor entirely independent of genes) to calculate a polygenic risk (i.e. summarising the combined influence of your genes on your probability of developing a given disease in a single figure) in over 500 healthy individuals, the majority of whom were young adults (aged 18 to 31), but also included older people (aged 50 to 69). Before continuing, it is important to note that the polygenic risk remains low and cannot predict who will develop the disease. Using this risk estimate, the team looked for correlations with the participants' sleep characteristics.

The results show that, in this case, the genetic risk of developing Alzheimer's disease is linked to the frequency of nocturnal micro-awakenings – brief periods of brain activity that do not fully wake the sleeper but can disrupt the sleep cycle. No such link was found among the younger participants. Among older participants, however, more frequent micro-awakenings go hand in hand with a higher genetic risk, even though they are still relatively young and show no signs of the disease.