This Sleep Habit Increases the Risk of Dementia by 27%

How to Reverse the Damage Starting Tonight

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My Longevity Experiment
February 19, 2025

The Link Between Slow-Wave Sleep and Dementia Risk in Older Adults

A recent study published in JAMA Neurology has revealed a significant connection between slow-wave sleep loss and the risk of dementia. Individuals over the age of 60 who lose just 1 percent of their deep sleep each year face a 27 percent increased likelihood of developing dementia.

Understanding Slow-Wave Sleep

Slow-wave sleep is the third stage of a typical 90-minute sleep cycle, lasting between 20 and 40 minutes. It is the most restorative phase, characterized by reduced brain wave activity, lower heart rate, and decreased blood pressure. This stage plays a crucial role in strengthening muscles, bones, and the immune system while also preparing the brain for optimal cognitive function.

Recent findings indicate that individuals exhibiting Alzheimer's-related changes in the brain perform better on memory tests when they achieve higher levels of slow-wave sleep.

"Slow-wave sleep, or deep sleep, supports the aging brain in many ways, and we know that sleep augments the clearance of metabolic waste from the brain, including facilitating the clearance of proteins that aggregate in Alzheimer's disease," said neuroscientist Matthew Pase from Monash University in Australia.

"However, to date we have been unsure of the role of slow-wave sleep in the development of dementia. Our findings suggest that slow-wave sleep loss may be a modifiable dementia risk factor."

Study Findings on Sleep and Dementia Risk

Pase and a team of researchers from Australia, Canada, and the United States analyzed data from 346 participants of the Framingham Heart Study. These individuals had undergone two overnight sleep studies between 1995 and 1998 and again between 2001 and 2003, with an average five-year gap between assessments. At the time of the second sleep study, none of the participants had been diagnosed with dementia. Researchers then monitored them for dementia until 2018.

"We used these to examine how slow-wave sleep changed with aging and whether changes in slow-wave sleep percentage were associated with the risk of later-life dementia up to 17 years later," Pase explained.

Over the 17-year follow-up period, 52 participants developed dementia. The data showed that slow-wave sleep declines progressively from age 60 onward, peaking in decline between ages 75 and 80 before stabilizing.

By analyzing changes in slow-wave sleep between the two sleep studies, researchers determined that each percentage point decrease in slow-wave sleep per year corresponded to a 27 percent higher risk of developing dementia. The risk was even greater—32 percent—when specifically examining Alzheimer's disease, the most common form of dementia.

Genetic and Cardiovascular Links to Sleep Decline

The Framingham Heart Study, which tracks various health metrics over time, also examined links between slow-wave sleep and other factors such as hippocampal volume loss (an early indicator of Alzheimer's disease) and cardiovascular health.

Low levels of slow-wave sleep were associated with a higher risk of cardiovascular disease, certain medications that affect sleep quality, and the presence of the APOE ε4 gene, a known genetic risk factor for Alzheimer's disease.

"We found that a genetic risk factor for Alzheimer's disease, but not brain volume, was associated with accelerated declines in slow-wave sleep," Pase stated.

Implications for Sleep and Brain Health

Although this study establishes a clear association between slow-wave sleep loss and dementia risk, the researchers caution that it does not prove causation. It remains possible that underlying dementia-related brain changes contribute to sleep loss rather than sleep loss being a direct cause of dementia. Further research is needed to fully understand this relationship.

In the meantime, prioritizing quality sleep is essential for overall health and cognitive function. Taking steps to optimize sleep—such as maintaining a consistent sleep schedule, reducing exposure to screens before bedtime, and managing stress—can support long-term brain health and potentially reduce the risk of dementia.

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