Side sleeping is the best position for most people. It keeps your airway open, reduces snoring, and works well for acid reflux and pregnancy. But the ideal position for you depends on what your body is dealing with, whether that’s back pain, shoulder trouble, sleep apnea, or heartburn. Here’s what each position does well, where it falls short, and how to make any of them work better.
Side Sleeping: The Most Versatile Option
Sleeping on your side is the go-to recommendation from most sleep specialists, and it’s also the position most adults naturally prefer. It keeps the airway open by preventing the tongue and soft tissues in the throat from collapsing backward, which is why it’s the first-line suggestion for people who snore or have obstructive sleep apnea. A meta-analysis in Sleep Medicine Research found that avoiding the back position reduced breathing interruptions during sleep by about 54%.
Which side matters, too. Sleeping on your left side discourages acid reflux by making it harder for stomach acid to creep past the valve between your stomach and esophagus. If you deal with nighttime heartburn, this one change can make a noticeable difference. Left-side sleeping is also the recommended position during pregnancy because it promotes the best blood flow to the baby and helps prevent swelling in the legs and ankles.
The tradeoff is pressure on your joints. Your spine isn’t perfectly aligned on your side, so the position can concentrate stress on your neck, hips, or whichever shoulder is bearing your weight. People with shoulder injuries or rotator cuff problems often can’t tolerate sleeping on the affected side for long. If your bad shoulder is the one facing up, use a pillow to keep that arm straight and in a neutral position rather than letting it droop across your body.
Back Sleeping: Best for Spinal Alignment
If you have neck or back pain and no breathing issues, sleeping on your back is worth trying. It distributes your weight evenly and eliminates the sideways forces on your spine that side sleeping creates. Many people wake up with less stiffness in their neck, back, and hips when they sleep face-up.
The downsides are significant for certain groups, though. Back sleeping is one of the worst positions for snoring and sleep apnea. Gravity pulls all the soft tissue in your throat downward, narrowing or blocking the airway. One sleep specialist describes it as the tissue falling back “like a cork.” People who carry extra weight around their midsection, or who have heart failure or lung conditions, may also feel short of breath on their back because the position makes it harder to fully expand the lungs.
Back sleeping also worsens heartburn by making it easier for stomach acid to travel upward. And it’s not recommended during the second and third trimesters of pregnancy. The weight of the growing uterus presses on the inferior vena cava, the major vein that returns blood from the lower body to the heart, which can reduce blood flow to both you and the baby.
Stomach Sleeping: Proceed With Caution
Only about 10% to 20% of adults prefer sleeping on their stomachs, and most sleep experts advise against it. The position forces you to turn your head to one side for hours, straining the neck. It also tends to flatten or exaggerate the curve of the lower back, which can lead to soreness over time.
Stomach sleeping is particularly hard on shoulders. It’s common to tuck an arm under your pillow in this position, which puts the shoulder in an internally rotated, compressed position all night. One orthopedic specialist at the Cleveland Clinic calls this “shoulder problem city” because it sets the stage for rotator cuff issues.
If you simply can’t fall asleep any other way, you can reduce the damage. Place a thin pillow (or no pillow) under your head to keep your neck closer to neutral, and put a small pillow under your pelvis or lower belly to maintain the natural arch of your lower back.
How to Optimize Any Position With Pillows
The right pillow setup can turn a decent sleeping position into a great one. The goal is always the same: keep your spine in a neutral line from your head through your hips.
- Back sleepers: Place a pillow under your knees and a small roll under the curve of your neck. The knee pillow takes pressure off the lower back by flattening the lumbar curve slightly, and the neck roll prevents your head from tilting forward or backward.
- Side sleepers: Use a pillow thick enough to fill the gap between your ear and the mattress so your neck stays level with your spine. Place a second pillow between your knees to keep one leg from pulling your pelvis out of alignment. During pregnancy, adding a pillow under the belly provides extra support and helps maintain a comfortable side tilt.
- Stomach sleepers: Use the thinnest pillow you can tolerate under your head, or skip it entirely. A small pillow under the lower abdomen helps prevent the hips from sinking too deep.
Mattress Firmness by Position
Your mattress matters as much as your position. Side sleepers generally do best on a softer mattress (roughly a 1 to 3 on a 10-point firmness scale) because it lets the shoulders and hips sink in enough to keep the spine straight. A mattress that’s too firm creates pressure points at those two spots, which is why side sleepers often wake up with sore hips or numb arms.
Back and stomach sleepers need the opposite: a medium-firm to firm mattress (around 7 to 10 on the scale) that prevents the hips from sagging. When your midsection dips into a too-soft mattress, your lower back arches unnaturally, and you wake up stiff. This is especially true for stomach sleepers, where a soft mattress turns the lower spine into a hammock shape all night.
Choosing a Position for Specific Conditions
If you have heart failure, right-side sleeping is often more comfortable than left. People with heart failure frequently experience worsening shortness of breath when they lie on their left side, likely because of how the position shifts the heart’s position relative to the chest wall. Many naturally gravitate to their right side or to a slightly elevated back position.
For sleep apnea, side sleeping is the single most effective positional change you can make. Studies show that people with position-dependent sleep apnea (where breathing events at least double on the back compared to other positions) can see reductions of 69% to 79% in their breathing interruptions just by staying off their back. Special pillows or wearable devices that discourage rolling onto your back can help if you tend to shift positions during the night.
For shoulder pain, the instinct is to sleep on the opposite side, but even back sleeping can cause problems. Lying flat on your back lets the affected shoulder sag slightly toward the mattress, enough to strain the rotator cuff. Resting the arm on a folded blanket or low pillow while on your back keeps the shoulder supported and in a more neutral position.
For lower back pain, back sleeping with a pillow under the knees is typically the gentlest option. Side sleeping with a pillow between the knees is a close second. Stomach sleeping tends to be the most aggravating for the lower back, though the pelvis pillow trick helps if you can’t break the habit.