Most people focus on how many hours of sleep they get each night but a new study suggests that the type of sleep you’re getting may matter just as much, if not more, when it comes to long term brain health. Researchers have found that consistently getting less deep sleep and less REM sleep may be associated with changes in the brain that mirror the earliest signs of Alzheimer’s disease.
What researchers studied and what they found
The study followed 270 middle-aged and older adults, most of whom were in their early 60s at the start of the research. Each participant completed an overnight sleep study to measure how much time they spent in different sleep stages, with particular attention paid to slow wave sleep commonly called deep sleep and REM sleep.
Between 13 and 17 years later, the same participants underwent brain scans to assess the size of specific regions known to be vulnerable in Alzheimer’s disease. Two regions were of particular interest, the inferior parietal lobule, and the precuneus. Both play important roles in memory, attention and spatial reasoning functions that tend to deteriorate in the early stages of dementia.
The researchers were looking for a long term relationship between the quality of someone’s sleep years earlier and their brain volume at the time of the scan. That connection proved to be real.
How less deep and REM sleep affected the brain
People who spent less time in slow wave sleep and REM sleep were more likely to show shrinkage in brain regions associated with early Alzheimer’s. Specifically, reduced time in deep sleep was tied to smaller volumes in the inferior parietal and cuneus regions, while reduced REM sleep was linked to smaller volumes in the inferior parietal and precuneus areas two of the regions that tend to decline first as Alzheimer’s progresses.
It’s worth noting that the study did not prove that poor sleep caused these brain changes. However, the association was strong enough to be clinically notable, particularly because it spans such a long follow-up window.
Why deep sleep is so important for brain health
These findings add to a growing body of research that points to deep sleep as a key period for brain maintenance. During slow wave sleep, the brain’s glymphatic system a kind of internal rinse cycle works to clear out metabolic waste, including beta amyloid, the protein that accumulates in the brains of people with Alzheimer’s disease.
Prior research has shown that even a single night of disrupted deep sleep can lead to increased beta amyloid buildup. Over years or decades, chronic shortfalls in these restorative sleep stages could, according to researchers, contribute to the kind of structural brain changes observed in this study.
5 science backed habits to protect your deep and REM sleep
While it isn’t yet possible to control sleep architecture with complete precision, several well-supported strategies may help increase the proportion of time spent in deep and REM sleep.
Keep a consistent sleep schedule. Going to bed and waking up at the same time each day including weekends helps regulate sleep cycling and supports more time in restorative stages.
Cut off caffeine early. Caffeine consumed too close to bedtime can suppress deep sleep. Limiting intake to the first half of the day is a practical and effective step.
Get morning sunlight. Early light exposure helps anchor the body’s circadian rhythm, which in turn supports better overall sleep quality and structure throughout the night.
Exercise regularly. Both aerobic exercise and resistance training have been shown to increase the proportion of slow wave and REM sleep over time, another reason physical activity is good for the brain.
Minimize alcohol close to bedtime. While alcohol may make it easier to fall asleep initially, it disrupts REM sleep during the second half of the night, reducing the restorative value of the overall sleep cycle.
The bottom line
This research is a meaningful reminder that sleep quality is not just about feeling rested the next morning. The two specific sleep stages examined deep sleep and REM sleep appear to have a long term relationship with the structural integrity of brain regions that are among the first affected by Alzheimer’s disease. The habits built around sleep today may have measurable consequences for brain health years down the line. Prioritizing both the quantity and the quality of sleep, particularly these restorative stages, is one of the more accessible and evidence backed steps available for protecting cognitive health as you age.
