One thing is very clear. If you are a baby, you should be sleeping on your back. Infants who sleep on their back, as opposed to their stomachs, have a reduced risk of sudden infant death syndrome (SIDS). The axiom of “Back to Sleep, Front to Play,” or the somewhat more prosaic French version of “Dodo sur le Dos,” is widely accepted and has largely contributed to the decrease in SIDS seen over the past decade.
However, if you are reading this article you are likely not a baby, and as fully-grown presumably potty-trained adult, your sleep position probably does not matter all that much.
There are a few situations where one particular sleep position may make a difference. For example, people with back or hip problems may find one position more comfortable than another. Sleeping on your side with a pillow between your legs may take some pressure off your hip, while sleeping on your stomach may strain your lower back. Snoring is often worse when people sleep on their back and somewhat relieved if they sleep on their side. People who suffer from acid reflux have undoubtedly realized that acid is more likely to leak up into their esophagus if they lie flat and that the symptoms are a bit better if they prop themselves up on a few pillows, thereby using gravity to their advantage.
Leg swelling inevitably gets better if you sleep with a slight elevation to your legs. But people with congestive heart failure often find their breathing is worse if their head is down and find relief if they can sleep in a semi-sitting position because gravity will draw fluid away from their lungs. This phenomenon is called orthopnea, which comes from the Greek orthos- (straight or upright) and –pnea(to breathe) and it is a common signal of worsening heart failure. It is the exact opposite of the condition of platypnea, where breathing is better when lying down. This is much rarer and generally results from a congenital cardiac defect where blood is shunted from the right side of the heart to the left.
So there are certainly a few situations where one sleep position will be better, or at least more comfortable, for you than another. But one question I often get asked in clinic is whether sleeping on the right or the left affects the heart in any major way.
The only real situation where sleep position could affect cardiac function is with aortocaval compression syndrome. Aortocaval compression syndrome (sometimes also called supine hypotensive syndrome) can occur in pregnant women when an enlarged uterus pushes on and compresses the large blood vessels in the abdomen like the aorta and inferior vena cava. This can impair blood flow to the heart and cause low blood pressure, which in turn leads to impaired blood flow to the fetus. The usual solution is to have the pregnant woman turn onto her left side, thus off-loading the uterus and restoring blood flow. It’s not clear from the research how common this phenomenon actually is in the population at large, although it is probably quite rare. Still, pregnant women are sometimes advised to sleep on their left side. Although, my informal canvas of colleagues with children suggests that most pregnant women sleep on their sides regardless, and change positions multiple times during the night anyway.
But for the non-pregnant among you, sleeping on your right or left is unlikely to have any impact. People often tell me that they are more likely to feel palpitations when sleeping on one side or the other. More often than not, they say that they are more likely to feel palpitations when lying on their left. This undoubtedly occurs, because when we turn on the left side, the heart lies closer to the chest wall and makes any skipped beats are more likely to be heard. Physicians sometimes ask patients to turn onto their left side to make certain heart sounds easier to hear for the same reason.
While it may be concerning to feel palpitations more often at night, it is usually not dangerous. Palpitations generally occur randomly throughout the day and we simply do not feel most of them because we are distracted by the cacophony and chaos of daily life. It is only at night, when our daily distractions leave us alone, that we appreciate these symptoms more readily.
When it comes to sleep, the real issue is that we don’t get enough of it. So the best sleep position is probably the one where you turn your phone off and go to bed early.
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