Lack of Deep Sleep Increases Alzheimer’s Risk

Recent research is sharpening the focus on the link between deep sleep and Alzheimer’s disease. A long-term study has found that not getting enough time in the deeper stages of sleep — specifically slow-wave sleep (SWS) and rapid eye movement (REM) sleep — is associated with shrinkage in parts of the brain that are known to deteriorate early in Alzheimer’s.

The findings don’t just confirm what we’ve suspected — they also point to sleep quality as a potentially modifiable risk factor for Alzheimer’s. That means better sleep habits could play a role in protecting long-term brain health.

The Brain-Sleep Connection: What the Study Found

In a cohort of 270 participants tracked over 13 to 17 years as part of the Atherosclerosis Risk in Communities Study, researchers analyzed sleep patterns recorded through polysomnography and compared them to brain MRIs taken more than a decade later. They focused on specific regions vulnerable to Alzheimer’s, including the hippocampus, inferior parietal lobule, precuneus, and cuneus.

Participants who spent less time in SWS and REM sleep showed significantly smaller volumes in key brain areas. For example, every 1% drop in SWS was linked to a 44.18 mm³ smaller volume in the inferior parietal lobule.

Similarly, less REM sleep was associated with smaller volumes in both the inferior parietal region and precuneus. These changes align closely with early signs of neurodegeneration seen in Alzheimer’s.

Importantly, the arousal index — a measure of how often someone wakes up during sleep — did not show a meaningful association with brain atrophy. Nor did any of the sleep variables predict the presence of cerebral microbleeds, which are also linked to aging and dementia but were not the focus here.

Why Deep and REM Sleep Matter

Deep sleep isn’t just downtime. During slow-wave sleep, the brain carries out critical cleanup tasks — clearing out waste products, including potentially harmful proteins like beta-amyloid, which is strongly associated with Alzheimer’s.

REM sleep, on the other hand, supports memory consolidation and emotional processing. It’s also when the brain integrates sensory information and reinforces learning.

So it’s not surprising that brain regions responsible for complex functions like visuospatial awareness — such as the inferior parietal lobule — are especially affected by reductions in deep and REM sleep. This region synthesizes sensory input and plays a role in how we understand our environment, which often becomes impaired early in Alzheimer’s progression.

Can You Improve Deep Sleep?

The good news is that improving deep sleep isn’t as difficult as it might seem. Experts note that both deep and REM sleep depend more on consistent, high-quality rest than just spending extra hours in bed. In fact, routines and environment play a bigger role than duration alone.

Maintaining healthy sleep habits—like sticking to a regular bedtime, keeping the bedroom dark and quiet, and steering clear of screens, caffeine, or alcohol in the evening—can significantly impact how restorative your sleep is. Even small calming rituals, such as a warm shower or gentle stretching before bed, may support deeper sleep.

Still, it’s worth noting that as we age, getting the same amount of deep sleep becomes more challenging, making those healthy habits even more important.

Evidence shows that even small improvements in sleep quality can benefit cognitive function. A separate 2023 study even linked strong sleep habits with longer life expectancy — nearly five years for men and 2.5 years for women.

As Dr. Richard Issacson, a preventive neurologist, pointed out, clinical experience backs these findings. In his work with at-risk adults, deeper sleep has consistently predicted better brain volume and cognitive outcomes.

Bottom Line: The link between deep sleep and Alzheimer’s is real and measurable. While genetics and other risk factors remain important, sleep is one area we can actively work on. Making sleep a priority isn’t just about feeling rested — it could help protect your brain in the long run.

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