Missing This Type of Sleep Could Raise Dementia Risk 27%

You already know that getting enough sleep is important—but new research reveals that one specific stage of sleep may be essential for protecting your brain from dementia.

It’s called slow-wave sleep—the deepest, most restorative stage of your sleep cycle. And according to a 2023 study published in JAMA Neurology, just a 1% annual decline in this sleep phase can raise your risk of dementia by 27% after age 60.

That’s a startling statistic—and a wake-up call for anyone looking to protect their memory as they age.

Slow-wave sleep is the third stage of your 90-minute sleep cycle. It usually lasts about 20 to 40 minutes per cycle, and it’s when your heart rate slows, your blood pressure drops, and your brain gets to work clearing waste—including the sticky proteins that are hallmarks of Alzheimer’s disease.

In fact, researchers have recently shown that people with Alzheimer’s-like brain changes still perform better on memory tests when they get more slow-wave sleep.

“Slow-wave sleep, or deep sleep, supports the aging brain in many ways,” says neuroscientist Matthew Pase of Monash University in Australia. “Sleep augments the clearance of metabolic waste from the brain—including the clearance of proteins that aggregate in Alzheimer’s disease.”

But until recently, it wasn’t clear whether the loss of slow-wave sleep contributed directly to dementia risk… or was just a symptom of the disease.

Now we have some answers.

Pase and an international team of researchers used data from the Framingham Heart Study, a long-term project tracking brain and cardiovascular health. They analyzed two sleep studies conducted roughly five years apart for 346 participants—none of whom had dementia at the time.

Then, they followed these individuals for up to 17 years, watching to see who developed dementia.

They discovered that starting around age 60, participants lost slow-wave sleep as they aged—especially between the ages of 75 and 80. And the greater the annual loss of deep sleep, the higher the dementia risk:

• A 1% annual drop in slow-wave sleep was linked to a 27% increased risk of dementia.
• For Alzheimer’s disease specifically, the risk rose to 32%.

Even more interesting? The decline in deep sleep was linked to carrying the APOE ε4 gene (a known genetic risk factor for Alzheimer’s), but not to early signs of brain volume loss—suggesting sleep changes may precede structural brain damage.

This study doesn’t prove that poor sleep causes dementia. It’s possible the relationship goes the other way—that early Alzheimer’s brain changes begin to disturb deep sleep.

Still, the connection is strong enough to sound the alarm.

If you’re in your 60s or older—or have a family history of Alzheimer’s—prioritizing sleep may be one of the most powerful steps you can take to protect your brain. Even better? There are natural, actionable ways to boost your slow-wave sleep tonight.

Here are a few research-backed strategies for getting more deep sleep:

• Stick to a regular sleep schedule – Go to bed and wake up at the same time every day to support your body’s natural rhythms.
• Limit alcohol and caffeine – Both can reduce deep sleep quality and disrupt your sleep cycles.
• Exercise regularly – Physical activity, especially earlier in the day, is linked to better sleep depth and duration.
• Avoid screens before bed – Blue light can delay melatonin release and shorten deep sleep.
• Try natural supplements – Magnesium, L-theanine, and melatonin may promote relaxation and deeper sleep when used responsibly.

You can’t stop aging. But according to this latest research, you can slow down the brain changes that often come with it—by protecting your deep sleep.

If you’re over 60, don’t just count hours of sleep. Pay attention to quality—especially your time spent in slow-wave sleep. It may be one of the simplest, most natural tools we have to safeguard memory and reduce the risk of dementia.

To getting deep sleep,

Rachel Mace
Managing Editorial Director, e-Alert
with contributions from the research team

Sources:

Dyer, R. (2025, May 16). One Stage of Sleep Seems Critical For Reducing Risk of Dementia. ScienceAlert. https://www.sciencealert.com/one-stage-of-sleep-seems-critical-for-reducing-risk-of-dementia