Does It Really Matter Which Side You Sleep On?
I’m one of those people who can’t feel comfortable at night until I’ve changed every possible sleeping position, ideally twice. But when I was pregnant, I kept hearing the message that we should all sleep on our left side. On the other hand, there are studies suggesting that the right side may be better for people with certain medical conditions. Let’s consider all the factors and see if there is an optimal side for you .
Is it good or bad to sleep on your side?
If your sleeping position is comfortable and you don’t have any health problems that require you to change it, you can probably sleep the way you want.
However, side sleeping is often recommended as a good thing. If you’re pregnant, sleeping on your stomach is no longer an option. Sleeping on your back during pregnancy can impede blood flow since some of our major blood vessels—the aorta and vena cava—run along the back of the abdomen. When the uterus becomes large enough, it can put pressure on these blood vessels.
If you have obstructive sleep apnea , you will likely be advised not to sleep on your back, as people tend to have more episodes of apnea on their back. Sleeping on your back is also thought to increase snoring. (PSA: If you haven’t been tested for sleep apnea but find that you sleep better when you don’t lie on your back, you may want to get tested.)
And if you suffer from back pain, sleeping on your side is generally more comfortable than sleeping on your back or stomach, although this varies from person to person.
Why You May Want to Sleep on Your Left Side
The main reason to sleep on your left side is due to the shape of your stomach. If you imagine your belly as a round ball, immediately get that image out of your head. Not only is your stomach smaller than you probably think, it’s also asymmetrical. The esophagus (food tube) enters it from the right side. ( Here’s a diagram of the University of Rochester Medical Center showing exactly where it is and what its shape is.)
Because of this shape, lying on your left side means that it is easier for food and digestive juices to stay in the stomach where they belong. If you have GERD or get heartburn easily, sleeping on your right side can increase the chance of stomach acid moving up into your esophagus, making your heartburn worse.
(By the way, most of us have our bodies organized this way, but every once in a while someone’s organs end up in a position different from the one shown in the textbooks. A review published in the International Journal of Internal Medicine notes that a mirror image organ style is so rare that “[even] a busy surgeon may encounter this anomaly only once or twice in a lifetime.”)
Why You May Want to Sleep on Your Right Side
When you sleep on your left side, your stomach may be happier, but your heart changes position. The heart is located slightly to the left of the center of the chest, and in the very center of the chest there is a connective tissue structure called the mediastinum.
When you lie on your right side, the mediastinum holds the heart in place. But when you lie on your left side, your heart sags and rotates slightly. Most of the time this is not a problem for most of us, but the movement is significant enough to be detected by electrocardiogram readings .
For this reason, it is believed that the heart beats more efficiently when you lie on your right side than on your left. This in turn may help you breathe easier if you have sleep apnea . This may be why animal studies have shown that sleeping on your side can improve the clearance of “glymphatic” waste from the brain , one of the important maintenance tasks that occurs during sleep.
What to do if the above factors do not apply to you
First, if your doctor has told you to sleep in a certain position, follow his advice. However, if they want you to sleep in a position that you find uncomfortable or impractical, ask them why they recommend that position, as well as how important it is . Perhaps the recommendation is simply a suggestion of something they hope will make you more comfortable, rather than a medical necessity. The only way to know the difference is to ask.
For the rest of us, it’s usually quite normal to experiment with our sleep positions. While the shape of our heart and stomach may indicate that one position is better than another, we have complex bodies made up of many different parts. If you have an old shoulder injury that gets worse if you sleep on that side, you may want to avoid this position.
Ultimately, with the exception of certain positions for certain medical conditions, most of us can choose the most comfortable sleeping position, and for most of us it won’t make much of a difference. The Sleep Foundation says what’s best for you “depends on your personal preferences as well as the support of your mattress and pillow.” For troubleshooting, they offer a simple rule: “If you experience discomfort or pain, try a different sleeping position.”