As we age, the nights become shorter, but sleep is no less important for health. On the contrary, studies reveal that it helps limit memory loss.
During family vacations, many people have been woken up at dawn by their grandparents who were a little too early in the morning. Seniors are early risers because sleep time decreases as they age. Well, not quite. Seniors need the same amount of sleep as their younger counterparts 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, which are themselves divided into sleep phases. Each cycle lasts more or less 90 minutes and is “made up of an alternation of slow-wave sleep and paradoxical 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 muscular activity is slowed down. Paradoxical sleep corresponds to the period most conducive to dreams. During this stage of sleep, brain activity is greater.
However, with age, we notice that this cycle becomes disrupted, deep slow-wave sleep decreases while periods of paradoxical sleep intensify. A study published in 2023, also indicates that people over 60 are 27% more at risk of developing dementia if they lose even 1% of this stage of sleep each year.
“Slow wave, or deep, sleep supports the aging brain in many ways, and we know that sleep increases the removal of metabolic waste from the brain, including facilitating the removal of proteins that aggregate in Alzheimer’s disease ” said Matthew Pase, a neuroscientist at Monash University in Australia, who co-authored the study.
The results of research carried out by the University of Berkeley also indicate that “deep sleep could help alleviate memory loss in older people facing advanced stages of Alzheimer’s disease.” This second study explains that deep sleep would eliminate beta-amyloid proteins, present in the brain and which affect memory.
The accumulation of these proteins is due to poor quality sleep. And increasing the amount of deep slow-wave sleep would help limit their spread and act as “a protective factor against the decline of memory in people with Alzheimer’s” specifies the American study. If these findings are confirmed in further research, it may be possible in the future to alleviate some of the most devastating effects of dementia in sick people, because “sleep is something we can modify,” adds one of the authors of the study.