Side sleeping is the position most sleep and spine experts recommend for the majority of people, and it’s already how most of us naturally sleep. Roughly 71% of adults spend the night on their side. But the “best” position depends on what your body needs: back sleeping keeps your spine in the most neutral alignment, side sleeping helps with snoring and digestion, and stomach sleeping is generally the least recommended option. Here’s what each position actually does to your body and how to optimize whichever one you prefer.
Side Sleeping: The Most Recommended Position
Sleeping on your side checks the most boxes for the most people. It keeps your airway open better than back sleeping, which is why it’s the go-to recommendation for snoring and sleep apnea. People with positional sleep apnea experience breathing interruptions at twice the rate when they flip onto their back compared to sleeping on their side. If your partner complains about your snoring, switching to your side is the single easiest fix.
Side sleeping also appears to help your brain clean house overnight. Your brain has a waste-clearing system that flushes out metabolic byproducts, including the proteins linked to Alzheimer’s disease. Research published in the Journal of Neuroscience found this system works most efficiently in the lateral (side) position compared to sleeping on your back or stomach. The study tracked how quickly waste cleared from brain tissue and found that lying on your side produced less retention and faster removal of these byproducts.
The left side specifically has a digestive advantage. If you deal with heartburn or acid reflux, sleeping on your left side helps acid clear from your esophagus significantly faster than sleeping on your back or right side. The number of reflux episodes stays about the same regardless of position, but the burning sensation resolves more quickly on the left because of how your stomach and esophagus are oriented anatomically.
One group that benefits from the right side instead: people with heart failure often find that sleeping on the left side worsens shortness of breath, so they tend to be more comfortable on the right.
How to Set Up for Side Sleeping
The main risk of side sleeping is letting your spine sag or twist. Draw your legs up slightly toward your chest and place a pillow between your knees. This keeps your spine, pelvis, and hips aligned so one leg doesn’t pull your pelvis into a tilt. Don’t curl up too tightly, though. If your hips and knees flex too far, your lower spine rounds outward and you lose that neutral position.
Your pillow matters more in this position than any other. Side sleepers need a thicker pillow, around 4 to 6 inches, to fill the gap between the mattress and your head. A simple way to find the right height: measure the distance from your shoulder to your ear while lying down, and pick a pillow that fills that space without pushing your head up or letting it drop.
Back Sleeping: Best for Spinal Alignment
Sleeping on your back is the single best position for keeping your spine neutral. Your body weight distributes evenly, and nothing is twisted or compressed asymmetrically. For people with back pain or neck pain who can tolerate this position, it’s worth trying.
The setup is simple but important. Place a pillow under your knees to preserve the natural curve of your lower back. A small rolled towel under the hollow of your waist adds extra support if you need it. Your head pillow should be moderate in height, around 3 to 5 inches, just enough to keep your neck aligned with your chest and upper back without pushing your chin toward your chest.
The downside of back sleeping is gravity. When you’re face-up, your tongue and soft tissues fall backward, which narrows your airway. This is why back sleeping worsens snoring and sleep apnea. If you snore heavily or have been told you stop breathing in your sleep, back sleeping is the position to avoid. It’s also not recommended during late pregnancy, which we’ll get to below.
Stomach Sleeping: The Least Ideal Option
Stomach sleeping is the hardest position on your body. The core problem is your neck: you have to rotate your head fully to one side to breathe, which keeps your cervical spine twisted for hours at a time. This sustained rotation can lead to morning stiffness, neck pain, and discomfort that builds over time.
Your lower back takes a hit too. Lying face-down tends to flatten or even reverse the natural curve of your lumbar spine, which puts pressure on the joints and discs in that region. If you absolutely cannot fall asleep any other way, place a pillow under your hips and lower stomach to maintain some arch in your back. Use a very thin pillow for your head (under 2 to 3 inches) or skip the head pillow entirely to reduce the angle your neck has to hold.
Stomach sleeping does have one small advantage: it can reduce snoring in some people by keeping the airway from collapsing the way it does on your back. But side sleeping accomplishes the same thing without the spinal trade-offs.
Sleep Position During Pregnancy
After 28 weeks of pregnancy, going to sleep on your side is a meaningful safety measure. A large meta-analysis published in The Lancet found that women who fell asleep on their back in the third trimester had 2.6 times higher odds of late stillbirth compared to those who fell asleep on their left side. The researchers estimated that if every pregnant woman past 28 weeks settled to sleep on her side, late stillbirth rates could drop by nearly 6%.
The reason is mechanical. The weight of the uterus in late pregnancy compresses major blood vessels when you lie flat on your back, reducing blood flow to the placenta. Either side works, though the left is slightly preferred for circulation. The key detail: this applies to the position you fall asleep in. If you wake up on your back in the middle of the night, simply roll to your side and settle back in. Most people stay in their falling-asleep position for the longest stretch of the night.
How to Actually Change Your Sleep Position
Knowing the “best” position doesn’t help much if you can’t stay in it. Your body shifts 10 to 30 times per night, and you have no conscious control over most of those movements. The position you fall asleep in tends to be the one you spend the most time in, so that’s the one worth targeting.
If you’re trying to stop sleeping on your back, the classic trick is the tennis ball method: attach a tennis ball (or stuff a sock with two of them) to the back of your sleep shirt. It makes rolling onto your back uncomfortable enough that your body learns to avoid it without fully waking you. This is a standard recommendation for positional snoring and mild sleep apnea.
If you’re trying to move from stomach to side sleeping, a body pillow can help. Hugging a full-length pillow gives your arms and top leg something to rest on, mimicking some of the “cocooned” feeling stomach sleepers prefer without the neck rotation. It also makes it physically harder to roll fully onto your stomach.
Give any position change at least two to three weeks. The first few nights will feel awkward, and you’ll likely revert to your old position in your sleep. Consistency with the falling-asleep position is what gradually retrains your habits.
Matching Your Position to Your Pillow
The wrong pillow can cancel out the benefits of the right position. The goal is always the same: keep your head, neck, and spine in one straight line (or natural curve, in the case of back sleeping).
- Side sleepers need the thickest pillow, 4 to 6 inches, to bridge the gap created by the shoulder. Too flat and your head drops, straining the neck. Too thick and your head tilts upward.
- Back sleepers need a medium pillow, 3 to 5 inches, that supports the natural curve of the neck without pushing the head forward into a chin-to-chest position.
- Stomach sleepers need the thinnest option available, under 2 to 3 inches, or no pillow at all. Anything thicker forces the neck into extension.
If you switch positions throughout the night, a medium-loft pillow that compresses easily is a reasonable compromise. But if you consistently wake up with neck stiffness or headaches, your pillow height relative to your dominant sleeping position is the first thing to reassess.