(Montreal) A loss of only 1% of deep slow-wave sleep per year in people aged 60 and over increases their risk of dementia by 27%, warns a new study in which a Montreal researcher participated.
A night of sleep normally includes several phases of deep slow-wave sleep, which together represent about a fifth of the total sleep time.
“There were already many assumptions about the importance of deep slow-wave sleep for memory […] but this is the first time that we show that this loss of deep slow-wave sleep could be associated with an increased risk of developing Alzheimer’s disease years later,” summarized researcher Andrée-Ann Baril, from the University of Montreal.
Researchers examined just under 350 subjects aged 60 and over who participated in the Framingham Heart Study. The subjects participated in two sleep studies – the first between 1995 and 1998 and the second between 2001 and 2003 – with an average delay of five years between the two.
Signs of dementia were then monitored in these participants from the second study, up to 2018. Fifty cases of dementia were detected during 17 years of follow-up. Even taking into account factors such as age, sex, smoking, and the use of sleeping pills, antidepressants and anxiolytics, each one percent decline in deep sleep time increased the risk of dementia by 27%.
The exact nature of this association remains to be specified. However, researchers know that it is during the phase of deep sleep that the brain eliminates metabolic waste – such as proteins that accumulate in patients with Alzheimer’s disease. This could therefore mean that deep sleep is a modifiable risk factor for dementia.
“We think that there are several mechanisms of the restorative functions of sleep that happen during deep slow-wave sleep,” said Mmoi Baril. There is also an important role in synaptic plasticity and memory, in the consolidation of learning that takes place in deep sleep. ”
It is also not exactly known in which direction the association is made. Since Alzheimer’s disease develops over several years before the first symptoms appear, it is not impossible that the disease itself is responsible for the disruption of deep slow-wave sleep.
It can also be a vicious circle. We sleep a little less well, it affects the brain, which affects sleep, and so on. Our results suggest a significant association with deep slow-wave sleep, but that does not necessarily mean that it causes Alzheimer’s disease.
Andrée-Ann Baril, researcher at the University of Montreal
The scientific data available at the moment suggests that poorer quality sleep could facilitate the pathological processes of Alzheimer’s disease, she added, but early signs of Alzheimer’s could also affect sleep, “so there is a good chance that we are dealing with a vicious circle here.”
Other studies, however, have shown that regular physical activity can increase the amount of deep slow-wave sleep.
The conclusions of this study were published by the medical journal JAMA Neurology .
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2023-11-11 19:00:50
