You probably have a favorite way to fall asleep. Most of us settle into the same position every night without thinking twice. New research suggests that small choice may matter more than we realized.
Sleeping on your side may be the position that best helps the brain flush out amyloid-beta, a protein that builds up in Alzheimer's disease.
That finding comes from a study in the Journal of Neuroscience, published in August 2015 by researchers at Stony Brook University and the University of Rochester.
The team used contrast MRI to compare three sleeping positions. Lateral (on the side), supine (on the back), and prone (on the stomach). Glymphatic transport was most efficient in the lateral position.
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The study was conducted in rats and mice. That is important, because animal findings do not automatically apply to people.
What the glymphatic system actually does
The glymphatic system is the brain's overnight waste-clearance network. Cerebrospinal fluid moves through spaces around blood vessels and washes out proteins that pile up during the day.
Two of those proteins are amyloid-beta and tau. Both are strongly tied to Alzheimer's disease.
Most of this cleanup happens while you sleep. A 2025 review in Frontiers in Neurology reports the system is most active during the deepest stage of non-REM sleep, known as N3.
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Sleep deprivation slows the removal of amyloid-beta and tau. The same review confirms that lateral posture appears more efficient than sleeping on the back or the stomach.
Why the side may matter more than the pillow
The 2015 rodent study did not name a clear winner between left and right. Both lateral positions worked better than sleeping on the back or the stomach.
Human research on posture during sleep is still limited, and the scientists behind this work stress that the findings are early. Getting enough sleep, and enough deep sleep, is the more solid advice today.
Our earlier coverage explains how a specific type of deep sleep has been linked to lower Alzheimer's risk in people.
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Practical steps you can try tonight
If you already sleep on your side, keep going. If you tend to end up on your back or stomach, a body pillow behind the back can help you stay on your side through the night.
A pillow between the knees eases pressure on the hips and lower back. For shoulder pain from side sleeping, a slightly thicker pillow that keeps the head level with the spine can reduce the load on the down shoulder.
If your sleep is broken, if you snore heavily, or if a partner has noticed you stop breathing at night, talk to a doctor.
Sleep apnea and poor sleep quality both disrupt the brain's overnight cleanup. Treating them is likely to matter more than the exact side you lie on.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.