This stage of sleep is crucial for preventing Alzheimer’s: new study

The key to keeping your wits about you as you age may lie in shut-eye during midlife.

A study found that people over 60 who didn’t get enough slow-wave sleep — the third stage in the human sleep cycle — were at a higher risk of developing dementia.

Slow-wave sleep (SWS) — known as N3, delta sleep, and deep sleep — lasts roughly 20 to 40 minutes and precedes REM sleep. Experts agree SWS is critical to the body’s restoration and growth, bolstering the immune system, strengthening muscles and bones, slowing brain activity and reducing blood pressure.

The human sleep cycle lasts 90 minutes and repeats itself throughout each slumber session.

Researchers found that patients who lost just 1% of their slow-wave sleep each year were 27% more likely to develop dementia than their deep-sleeping cohorts.

Neuroscientist and researcher Matthew Pase from Monash University in Australia told Science Alert, “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.” 

Together with a team of international colleagues, Pase studied roughly 350 subjects who participated in two overnight sleep studies, one conducted between 1995 and 1998 and another between 2001 and 2003.

Researchers compared datasets from the two in-depth polysomnography sleep studies. Subjects over 60 as of 2020 who had no record of dementia during their 2001-2003 tests, were monitored for signs of cognitive decline until 2018.

This community-based cohort, who had no record of dementia at the time of the 2001-2003 study, and were over 60 years old in 2020, gave researchers a chance to look into the link between two factors over time by comparing the datasets from the two in-depth polysomnography sleep studies, and then monitoring for dementia among participants up until 2018.

Pase explained, “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. Our findings suggest that slow-wave sleep loss may be a modifiable dementia risk factor.”

Per a 2021 study and as previously reported by The Post, sleep deprivation in middle age increases the risk of cognitive decline, with results showing those who averaged less than six hours of shut-eye at ages 50, 60 and 70 were associated with a 30% higher dementia risk.

Another study found that middle-aged folk who experienced sleep disruption were at double the risk of cognitive decline than those who had the least sleep disruption.

In addition, and in a surprise to no one, lack of sleep can make you act selfish.

The authors of this latest study note that while there are clear associations between the loss of SWS and the development of dementia, it is possible that dementia-related brain processes both cause and are caused by sleep loss.

Pase stresses that more research is required but remains hopeful that this and future studies will help people better understand the relationship between sleep and cognitive health

It seems SWS is effective at both preventing and lessening the symptoms of cognitive decline, one 2023 study found that individuals with Alzheimer ‘s-related changes in their brain did better on memory tests when they got more slow-wave sleep.

Researchers at Penn State University recently defined four types of sleepers and how each slumber archetype affects long-term health.