A new study suggests that the quality of sleep may be more important for long-term brain health than the total number of hours spent asleep. Researchers found that people who spent less time in deep sleep and REM sleep were more likely to show shrinkage in brain areas linked to Alzheimer’s disease.
The study followed 270 middle-aged and older adults, most in their early 60s at the start. Each participant completed an overnight sleep study to measure time spent in different sleep stages. About 13 to 17 years later, the same participants received brain scans to check the size of specific regions known to be vulnerable in Alzheimer’s disease.
These areas, the inferior parietal lobule and precuneus, are involved in memory, attention, and spatial reasoning. These functions tend to decline early in dementia. Researchers found that less deep sleep was tied to smaller volumes in the inferior parietal and cuneus regions. Less REM sleep was linked to smaller volumes in the inferior parietal and precuneus areas.
Study links sleep stages to brain shrinkage
The study did not prove that poor sleep caused the brain changes. But the connection was strong enough to raise concern, as these regions are among the first to decline in Alzheimer’s progression. The findings build on earlier research showing that deep sleep helps clear waste from the brain, including beta-amyloid, a protein that builds up in Alzheimer’s disease.
One earlier study found that a single night of disrupted deep sleep led to increased beta-amyloid accumulation. Other research shows that slow-wave sleep supports the glymphatic system, a process that may help prevent neurodegeneration.
Habits that may improve sleep quality
While people cannot control their sleep stages with total precision, some habits may help improve sleep architecture. Going to bed and waking up at the same time daily supports better sleep cycling. Avoiding caffeine too close to bedtime can help, as it can suppress deep sleep. Morning sunlight exposure helps anchor the circadian rhythm, which can improve sleep quality and structure. Regular aerobic and resistance training have been shown to increase the proportion of slow wave sleep and REM sleep over time. Limiting alcohol close to bed is also advised due to its negative effect on REM sleep.
The study provides evidence that sleep patterns could influence brain health years or decades later. Sleep is a modifiable factor. While people cannot change their genes or fully prevent age-related changes, supporting cognitive future by improving sleep quality and composition now is possible.
