Research findings strongly link sleep issues and dementia. In one study of nearly 8,000 adults, people ages 50 to 70 who regularly slept less than six hours per night had a 30 percent higher risk of developing dementia than those who slept the seven hours or more recommended by the Centers for Disease Control and Prevention (CDC).
That said, researchers don’t yet know if poor sleep directly causes dementia, says Michelle Jonelis, MD, a board-certified sleep medicine physician at Lifestyle Sleep in Mill Valley, California. In some cases, sleep problems may be an early sign of dementia onset.
But scientists have discovered a few plausible mechanisms.
During deep, slow-wave sleep, the brain clears waste proteins like amyloid and tau — by-products of normal brain activity that can build up during waking hours. When sleep is too short or frequently interrupted, the brain may not perform this “cleaning” as effectively, says Dr. Dasgupta. Over time, if these proteins aren’t removed efficiently, they can clump together and form the plaques and tangles characteristic of Alzheimer’s disease.
A shortage of rapid eye movement (REM) sleep, which is the final stage of sleep and supports memory and emotional processing, may also contribute, Dasgupta notes. Emerging research supports this idea: In one long-term study of middle-aged adults, individuals who spent less time in REM sleep exhibited more shrinkage 13 to 17 years later in the parietal lobe, a brain region that is particularly vulnerable to Alzheimer’s disease.
The bottom line: Sleep problems don’t automatically lead to dementia, but consistently poor, disrupted, or untreated sleep may increase risk over time, making healthy sleep a worthwhile goal for brain health.