As people age, the likelihood of developing dementia could increase if they do not obtain sufficient slow-wave sleep. A study conducted in 2023 revealed that individuals over the age of 60 face a 27 percent higher risk of dementia for every 1 percent decrease in this essential deep sleep annually.
Slow-wave sleep is the third phase of a typical 90-minute sleep cycle, lasting about 20 to 40 minutes. This stage is when we rest the deepest. Brain activity, heart rates, and blood pressure decrease during slow-wave sleep. Deep sleep is important for strengthening our muscles, bones, and immune system, and it helps our brains learn new information better.
Recent studies show that people with Alzheimer ‘s-related brain changes performed better on memory tests when they had more slow-wave sleep.
Deep sleep benefits the aging brain in many ways, including helping to clear out waste and proteins linked to Alzheimer’s, according to neuroscientist Matthew Pase from Monash University in Australia. However, we haven’t fully understood how slow-wave sleep affects dementia progression.
Pase’s research suggests that less slow-wave sleep might be a risk factor for dementia that we can change. Pase and his team from Australia, Canada, and the US studied 346 participants from the Framingham Heart Study.
These participants had two overnight sleep evaluations between 1995-1998 and again between 2001-2003, with an average gap of five years between tests.
None had documented cases of dementia during the later study period, and all were over 60 years old by 2020. This allowed researchers to explore the link between sleep and dementia over time by analyzing data from both sleep studies while tracking dementia cases until 2018.
Pase stated, We utilized these to investigate the alterations in slow-wave sleep as individuals age and to determine if variations in the percentage of slow-wave sleep are linked to the likelihood of developing dementia later in life, even up to 17 years afterward.
In general, the amount of slow-wave sleep experienced by individuals begins to decline after the age of 60, with the most significant reduction occurring between ages 75 and 80 before stabilizing.
Researchers found a correlation between each percentage point drop in slow-wave sleep per year and a 27 percent higher likelihood of developing dementia when they analyzed the results from participants’ initial and follow-up sleep studies.
This risk escalated to 32 percent when focusing specifically on Alzheimer’s disease, which is the predominant type of dementia. The Framingham Heart Study tracks various health metrics over time, including reductions in hippocampal volume (an early indicator of Alzheimer’s) as well as factors that contribute to heart disease.
Lower slow-wave sleep levels were associated with an increased risk for cardiovascular disease, usage of medications affecting sleep patterns, and possession of the APOE 4 gene linked to Alzheimer’s.
Pase noted that while we identified a genetic risk factor for Alzheimer’s disease related to faster declines in slow-wave sleep, brain volume itself was not a contributing factor.
Despite these notable associations, the authors emphasize that this study does not establish causation between reduced slow-wave sleep and dementia; it remains possible that processes related to dementia may lead to diminished sleep quality.
Further research is necessary for a comprehensive understanding of these dynamics. In the meantime, prioritizing adequate sleep is essential not only for memory enhancement but also for overall health; there are even strategies available to increase your chances of achieving more vital slow-wave sleep.
The findings have been published in JAMA Neurology.