A recent study suggests that the quality of sleep, specifically the time spent in deep and REM stages, may be more important for long-term brain health than the total number of hours slept. Researchers followed 270 adults, most in their early 60s, for over a decade to examine the link between sleep and brain structure.
At the start of the study, each participant underwent an overnight sleep study to measure their time in different sleep stages. Between 13 and 17 years later, the same participants received brain scans. The scans focused on the size of brain regions known to be vulnerable in Alzheimer’s disease, including the inferior parietal lobule and precuneus. These areas are involved in memory, attention, and spatial reasoning.
The findings showed a clear pattern. People who spent less time in slow wave sleep, also known as deep sleep, were more likely to have shrinkage in the inferior parietal and cuneus regions. Those with less REM sleep showed smaller volumes in the inferior parietal and precuneus areas. The study did not prove that poor sleep directly caused these brain changes, but the connection was strong enough to raise concern.
These results build on earlier research. Previous studies have shown that deep sleep helps clear waste from the brain, including beta-amyloid, a protein linked to Alzheimer’s. One study found that a single night of disrupted deep sleep led to an increase in beta-amyloid accumulation. Another study indicated that slow-wave sleep supports the glymphatic system, which acts as a cleaning mechanism for the brain.
While people cannot fully control their sleep architecture, certain habits may help improve the quality of rest. Going to bed and waking up at the same time each day supports better sleep cycling. Avoiding caffeine late in the day is recommended, as it can suppress deep sleep. Morning sunlight exposure helps anchor the body’s circadian rhythm, which can improve sleep quality. Regular aerobic and resistance training have been shown to increase the proportion of slow wave and REM sleep over time. Limiting alcohol close to bedtime is also advised because of its negative effect on REM sleep.
The study adds to the evidence that sleep quality can influence brain health years later. Unlike genetics or age, sleep is a factor people can modify. Supporting deep and REM sleep now may help protect cognitive function in the future.
