The risk of developing dementia may increase with age if a person does not get enough slow-wave (deep) sleep. A 2023 study found that people over 60 are 27% more likely to develop dementia with a loss of just 1% of deep sleep each year.
REM sleep is the third stage of the 90-minute sleep cycle, lasting about 20-40 minutes. This is the most restorative stage, during which brain waves and heart rate slow down and blood pressure drops.
Deep sleep strengthens muscles, bones, and the immune system, preparing the brain to absorb new information. Recent studies have shown that people with signs of Alzheimer’s-related brain changes performed better on memory tests if they had more slow-wave sleep.
«Slow-wave sleep supports the aging brain and helps clear metabolic waste, including proteins that build up in Alzheimer’s disease,» said neuroscientist Matthew Pace of Monash University in Australia.
«Until now, we did not know whether slow-wave sleep plays a role in the development of dementia. Our findings suggest that the loss of this sleep may be a modifiable risk factor for dementia».
Pace and his colleagues from Australia, Canada, and the United States analyzed data from 346 participants in the Framingham Heart Study who underwent two overnight sleep studies between 1995 and 1998 and 2001 and 2003, with an interval of 5 years.
This sample, free of signs of dementia at the time of the study in 2001-2003 and over 60 years of age in 2020, allowed the researchers to trace the link between changes in deep sleep and dementia risk by tracking participants through 2018.
«We used these data to investigate how slow-wave sleep changed with age and whether changes in its levels were associated with the risk of dementia in later life up to 17 years later,» Pace said.
Over the 17 years of follow-up, 52 cases of dementia were recorded among the participants. The level of deep sleep in these participants was also correlated with dementia cases.
It was found that the level of slow-wave sleep begins to decline with age after 60 years, reaching a peak loss between 75 and 80 years, and then stabilizes.
Comparing the data from the first and second studies, the researchers found that each 1% decrease in REM sleep each year was associated with a 27% increase in the risk of developing dementia. This risk increased to 32% when focusing on Alzheimer’s disease, the most common form of dementia.
The study also links low levels of deep sleep to a higher risk of cardiovascular disease, taking medications that affect sleep, and having the APOE ε4 gene associated with Alzheimer’s disease.
While these are clear links, the authors note that this type of study does not prove that loss of deep sleep causes dementia. It is possible that processes associated with dementia cause sleep to deteriorate. Further research is needed to fully understand these factors.
Source: sciencealert
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