This stage of sleep is crucial for reducing the risk of dementia

As we age, nights get shorter, but sleep is no less important for our health. ;eacute;. On the contrary, studies reveal that it would contribute to limit memory loss.

Many people on family vacations have been woken up at the crack of dawn by their grandparents who were a bit too early. Older people are early risers because sleep time decreases as they get older. Well, not quite. Seniors need the same amount of sleep as their younger siblings, but their sleep period is more fragmented, especially with naps. In reality, with age, it is not the amount of sleep that decreases but its quality.

A night's sleep is divided into several cycles, themselves divided into sleep phases. Each cycle lasts approximately 90 minutes and is “made up of alternating slow-wave sleep and REM sleep, each corresponding to a different brain activity,” explains the National Institute of Health and medical research (Inserm).

Slow wave sleep itself has three stages: stage 1, during which the transition from wakefulness to sleep occurs, stage 2, known as “light sleep”, and stage 3, which corresponds to “deep sleep” during which brain and muscle activity slows down. REM sleep corresponds to the most dream-prone period. During this stage of sleep, brain activity is higher.

Or with age, we notice that this cycle becomes disrupted, deep slow sleep decreases while periods of REM sleep intensify. A study published in 2023 also indicates that people over 60 are 27% more likely to risk of developing dementia if they lose just 1% of this stage of sleep each year.

“Slow-wave sleep, or deep sleep, supports the aging brain in many ways, and we know that sleep increases the brain's clearance of metabolic waste products, including facilitating the removal of proteins that aggregate in Alzheimer's disease,” said Matthew Pase, a neuroscientist at the University of Monash in Australia, which co-authored the study.

Research findings from the University of Berkeley also indicate that “deep sleep may help alleviate memory loss in older people with advanced Alzheimer's disease.” This second study explains that deep sleep would eliminate beta-amyloid proteins, present in the brain and which would affect memory.

The accumulation of these proteins would be due to poor quality sleep. And increasing the quantity slow-wave sleep would help limit their spread and act as a “protective factor against memory decline in people with Alzheimer's,” the American study says. If these results are confirmed in further research, it will be In the future, it may be possible to mitigate some of the most devastating effects of dementia in people with the condition, because “sleep is something we can change,” adds one of the study's authors.