There is no single best sleeping position for everyone. Side sleeping, specifically on the left side, offers the widest range of health benefits for most people, which may explain why more than 60% of adults already sleep this way. But the ideal position depends on your body, your health conditions, and what you’re trying to improve or avoid.
Side Sleeping Has the Most Benefits
Side sleeping checks the most boxes for most people. Your airway stays more open than it does on your back, your spine can maintain a relatively neutral curve, and your digestive system works in your favor if you choose the left side. It’s also the position your body gravitates toward naturally. Research published in the Journal of Neuroscience found that your brain’s waste-clearance system, which flushes out harmful proteins while you sleep, works most efficiently in the lateral (side) position compared to sleeping on your back or stomach. This waste removal includes amyloid-beta, a protein linked to Alzheimer’s disease.
Left-side sleeping specifically helps with acid reflux. When you lie on your left side, your stomach sits below your esophagus, making it harder for acid to travel upward. Studies from Amsterdam UMC also found that when acid does reach the esophagus in this position, it drains back into the stomach more quickly. If you deal with heartburn or GERD, this simple switch can make a noticeable difference at night.
The left side is also the recommended position during pregnancy, particularly in the third trimester. It allows the most blood flow to the baby by keeping the weight of the uterus off the large vein that returns blood to the heart.
One exception: people with heart failure often feel more short of breath sleeping on the left side and tend to be more comfortable on their right, according to the American Heart Association.
The Downsides of Side Sleeping
Side sleeping puts direct, sustained pressure on whichever shoulder and hip are against the mattress. Over time, this can aggravate conditions like rotator cuff tendinitis, bursitis, shoulder impingement, and arthritis. If you already have shoulder pain, sleeping on the affected side compresses the joint for hours and often makes things worse.
Your face also pays a price. Pressing one side of your face into a pillow creates shear, compression, and tensile forces on the skin. Over years, this mechanical distortion contributes to sleep wrinkles, which form at locations where the skin buckles under external pressure and can reinforce existing expression lines. These forces are completely different from the gravitational pull your face experiences while standing, and they accumulate over the roughly one-third of your life spent sleeping.
How to Make Side Sleeping More Comfortable
Pillow height matters more than most people realize. A side sleeper’s pillow needs to fill the gap between the mattress and the head without bending the neck up or letting it droop down. Too high, and you strain the muscles in your neck and shoulders. A pillow height of 4 to 6 inches works for most people, though your frame and shoulder width will influence what feels right.
Placing a pillow between your knees keeps your hips stacked and prevents your top leg from pulling your spine out of alignment. If shoulder pressure is a problem, hugging a body pillow or placing a pillow between your arms helps keep the top shoulder in a neutral position rather than collapsing forward.
Back Sleeping and Spinal Alignment
Sleeping on your back distributes your body weight evenly and keeps your spine, neck, and head in a neutral position without any rotational stress. It’s the best position for minimizing pressure on any single joint, which makes it a good option if you have shoulder pain, hip pain, or general musculoskeletal issues. It’s also the only position that keeps your face free from contact with a pillow, making it the most effective way to prevent sleep wrinkles.
Your pillow should support the natural forward curve of your neck without pushing your head too far forward. A pillow under your knees can take pressure off your lower back by reducing the arch in your lumbar spine. This small adjustment makes back sleeping significantly more comfortable for people who find it strains their lower back.
When Back Sleeping Is a Problem
Back sleeping is the worst position for snoring and obstructive sleep apnea. Gravity pulls the tongue and soft tissues toward the back of the throat, narrowing the airway. In people with sleep apnea, respiratory events occur at roughly twice the frequency when lying on the back compared to other positions. If you snore heavily or have been diagnosed with sleep apnea, switching to side sleeping is one of the simplest interventions available.
Back sleeping also tends to worsen acid reflux, since the stomach and esophagus sit at roughly the same level, making it easier for acid to escape upward.
Stomach Sleeping: The Position to Avoid
Stomach sleeping is the hardest position on your body. Your torso is the heaviest part of you, so it sinks deeper into the mattress, causing your back to arch and pulling your spine out of its natural alignment. This creates strain across your lower back that can lead to pain and stiffness in the morning.
The bigger problem is your neck. You can’t breathe facedown into a pillow, so you have to turn your head to one side. This twists your cervical spine out of alignment with the rest of your back for hours at a time. Do this night after night, and you’re setting the stage for chronic neck pain and stiffness.
Research on the brain’s waste-clearance system found that the prone position (stomach down, head more upright) resulted in slower clearance and more “retention” of waste products compared to side sleeping. The face also endures the same compressive and shearing forces as side sleeping, if not more, since stomach sleepers often press their face directly into the mattress or pillow.
If you’re a committed stomach sleeper and can’t switch, using a very thin pillow (or no pillow at all) reduces the degree of neck extension. A pillow under your pelvis can also help keep your lower back from arching too deeply.
Choosing the Right Position for You
Your best sleeping position is shaped by what your body needs most. Here’s a quick breakdown:
- Acid reflux or GERD: Left side
- Snoring or sleep apnea: Either side
- Pregnancy (third trimester): Left side
- Heart failure: Right side
- Shoulder or hip pain: Back, or side sleeping off the affected joint
- Lower back pain: Back with a pillow under your knees
- Wrinkle prevention: Back
- General health with no specific concerns: Left side
Most people shift positions multiple times per night, and that’s normal. You don’t need to stay locked in one position from bedtime to morning. What you can control is which position you start in and whether your pillow setup supports it well. Small changes, like adding a knee pillow or switching from right to left, often make a bigger difference than people expect.