Sleeping on your side is not bad for you. It’s actually the most common sleep position, used by more than 60% of adults, and it offers several meaningful health benefits. That said, side sleeping does come with a few trade-offs worth knowing about, particularly for your shoulders, hips, and skin.
Why Side Sleeping Is Generally a Good Thing
Side sleeping keeps your airway open better than sleeping on your back or stomach. When you lie on your back, gravity pulls your tongue and the soft tissues at the back of your throat downward, which can partially block airflow. On your side, those tissues stay out of the way. This is why side sleeping reduces snoring and helps with obstructive sleep apnea.
There’s also evidence that side sleeping helps your brain clean itself more efficiently. During sleep, your brain flushes out metabolic waste through a drainage system that works like a rinse cycle. A study published in The Journal of Neuroscience found that this waste removal process, including clearance of proteins linked to Alzheimer’s disease, was most efficient when subjects were in the lateral (side) position compared to sleeping on the back or stomach. The researchers suggested that side sleeping may have evolved specifically to optimize this cleanup process.
Left Side vs. Right Side
Not all side sleeping is equal. The side you choose can make a real difference depending on your health.
Your left side is the better choice for digestion. The American Gastroenterological Association recommends left-side sleeping for people with acid reflux because gravity and the natural curve of your stomach work together to keep acid from creeping up into your esophagus. Right-side sleeping does the opposite, actually promoting acid flow into the esophagus and worsening reflux symptoms at night.
Your right side, however, may be better if you have heart failure. People with heart failure often feel more short of breath when lying on their left side. The American Heart Association notes that many of these patients naturally prefer sleeping on their right. If you have a healthy heart and no reflux issues, either side is fine.
The Shoulder and Hip Problem
The biggest downside of side sleeping is pressure. Your full body weight compresses into your shoulder and hip on whichever side you’re lying on, and your spine doesn’t naturally stay in a straight line in this position. Over time, or during a single night on a too-firm surface, this can lead to stiffness and pain.
If you already have a shoulder condition like bursitis, a rotator cuff tear, frozen shoulder, or impingement, sleeping on that side will almost certainly make it worse. The same applies to hip pain. People with arthritis or bursitis in one hip often find that side sleeping on that side becomes intolerable. The simplest fix is to sleep on the opposite side, though that’s easier said than done if you’re a creature of habit.
Your mattress matters here more than you might think. Side sleepers generally do best on a soft to medium-firm mattress that lets your shoulder and hip sink in slightly, keeping your spine level. A mattress that’s too firm creates hard pressure points at those two spots. A mattress that’s too soft lets your midsection sag, curving your spine in the wrong direction.
How to Align Your Spine While Side Sleeping
A pillow between your knees is one of the simplest improvements you can make. Without one, your top leg tends to fall forward, pulling your pelvis into a twist that rotates your lower spine. A firm pillow between the knees keeps your hips stacked and your pelvis neutral. Your upper thigh should be elevated enough that your hip stays level rather than angling downward.
If there’s a gap between your waist and the mattress when you lie on your side, a small rolled towel or thin pillow in that space can prevent your spine from bending laterally. Your head pillow also needs to be thick enough to fill the distance between your ear and the mattress so your neck stays straight. Too thin and your head drops; too thick and it pushes your head up at an angle. Both create neck strain by morning.
Side Sleeping and Wrinkles
This one surprises people, but it’s real. When you press your face into a pillow for hours each night, the mechanical compression and shearing forces on your skin create a distinct type of wrinkle. These “sleep wrinkles” show up most on the forehead, cheeks, and lips, and they differ from expression lines in an important way: they’re caused by physical pressure rather than muscle movement, so treatments like Botox don’t help with them.
Dermatologists and plastic surgeons have long advised patients to sleep on their backs to minimize this effect, but changing your sleep position is notoriously difficult. If this concerns you, a silk or satin pillowcase creates less friction than cotton, and some specialty pillows are designed to keep your face from pressing flat against the surface.
Side Sleeping During Pregnancy
Pregnant women are commonly told to sleep on their left side, especially in the third trimester. The reasoning is sound: the left side takes pressure off the large vein that returns blood from your lower body to your heart, promoting better blood flow to the uterus and reducing swelling in the legs and ankles.
That said, the concern about back sleeping causing stillbirth has been overstated. Experts at the University of Utah Health have noted that the data linking back sleeping to stillbirth is not strong enough to support that conclusion. The stress of trying to force yourself into an unnatural sleep position may be more harmful than occasionally rolling onto your back. A large multicenter trial involving roughly 10,000 first pregnancies is expected to provide clearer answers, but for now, left-side sleeping remains a reasonable default rather than a rigid rule.
Making Side Sleeping Work for You
For most people, side sleeping is a healthy position that supports breathing, digestion, and brain function during the night. The potential downsides, mainly joint pressure and skin compression, are manageable with the right setup. A supportive mattress, a pillow between the knees, and the correct head pillow height address the most common complaints. If you have shoulder or hip pain on one side, switching to the other side or adjusting your mattress firmness can make a noticeable difference without abandoning side sleeping altogether.