A new study from Yale School of Medicine has found that people who spend less time in deep sleep and dream-related sleep may have smaller brain regions that are known to be affected early in Alzheimer’s disease.
This suggests that not getting enough quality sleep could increase the risk of developing the disease later in life.
The study, published in the Journal of Clinical Sleep Medicine, looked at how specific stages of sleep are connected to long-term brain health.
It focused on two important sleep phases: slow wave sleep, which is the deepest stage of sleep, and REM sleep, the stage when most dreaming happens. These stages are believed to play a key role in brain repair, memory storage, and overall cognitive health.
Researchers analyzed sleep and brain data from 270 people, whose average age was 61 at the start of the study. More than half were women, and all participants were white. None of them had a history of stroke, dementia, or serious brain disorders when the study began.
Participants’ sleep patterns were measured using polysomnography, a detailed test that records brain waves, oxygen levels, heart rate, and breathing while a person sleeps.
More than a decade later—13 to 17 years after the sleep tests—the participants underwent brain scans to measure the size of different brain regions.
The researchers found that people who had spent less time in slow wave sleep and REM sleep years earlier had smaller volumes in parts of the brain, especially the inferior parietal region. This area of the brain is known to shrink early in people who go on to develop Alzheimer’s disease.
Importantly, the researchers adjusted the results to account for other factors that might influence brain health, such as age, sex, smoking, alcohol use, high blood pressure, and heart disease. Even after considering these factors, the connection between poor-quality sleep and smaller brain regions remained.
“These findings suggest that not getting enough restorative sleep might lead to brain shrinkage over time, especially in areas that are vulnerable to Alzheimer’s disease,” said Dr. Gawon Cho, the study’s lead author and a public health researcher at Yale.
Alzheimer’s disease is a progressive condition that slowly destroys memory and thinking abilities. It is the most common cause of dementia, and it affects an estimated 6.7 million older adults in the United States. Without major breakthroughs, that number could double by 2060.
Because sleep problems are common in middle-aged and older adults, this study raises an important question: could improving sleep help protect the brain from Alzheimer’s?
The authors believe that the structure of sleep, also known as sleep architecture, could be a modifiable risk factor—something that can be changed or improved to lower the risk of disease. For example, if doctors can help people get more deep sleep and REM sleep through better sleep habits or treatments, they may also be helping to protect those people’s brains.
However, the researchers were careful to say that their findings show a link—not direct proof—that poor sleep causes brain shrinkage or Alzheimer’s. More studies are needed to find out if improving sleep can actually slow or prevent the disease.
Still, this study adds to a growing body of research showing that good sleep is not just about feeling rested—it may be vital for keeping the brain healthy as we age.
Taking steps to improve sleep, such as following a regular sleep schedule, limiting screen time before bed, avoiding caffeine late in the day, and treating sleep disorders like sleep apnea, might be more important than we think—not just for how we feel tomorrow, but for how our brain functions years from now.
If you care about Alzheimer’s disease, please read studies that bad lifestyle habits can cause Alzheimer’s disease, and strawberries can be good defence against Alzheimer’s.
For more information about brain health, please see recent studies that oral cannabis extract may help reduce Alzheimer’s symptoms, and Vitamin E may help prevent Parkinson’s disease.
The research findings can be found in Journal of Clinical Sleep Medicine.
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