In February 2022, an online advertisement appeared to claim that sleeping on your right side (as opposed to your left or another position) could potentially be dangerous to your health. It read: "Experts Warn Not To Sleep On Your Right Side, Here's Why."
The Ad
The ad led to a 35-page slideshow article on the website Money Cougar.
One version of the ad appeared like this.The ad referred to "experts," but the Money Cougar article only mentioned one medical professional in reference to sleep positions. That expert was W. Christopher Winter, M.D.
Dr. Winter is a sleep specialist and neurologist at Charlottesville Neurology & Sleep Medicine. He's also the author of "The Rested Child" and "The Sleep Solution."
We reached out to Winter, and we also looked at the opinions of two other doctors regarding the subject.
'I Do Not WARN People'
The Money Cougar article cited data from a CNN story that was published in 2016. In that CNN story, Winter's expertise was cited many times.
In the CNN article, it said, "Side sleeping is by far the most commonly reported sleep position, and for good reason — it can have a whole lot of health benefits."
The story reported that snorers and those with breathing problems can benefit from side sleeping. It also said that side sleeping could be good for the brain and even give the spine "a break from the tension from holding your head up, standing or sitting throughout the day."
Similarly, sleeping on your left side, specifically, could help the flow of blood to your heart. When your heart pumps blood out to your body, it gets circulated and then flows back to your heart on the right side, Winter explains. If you sleep on your right side, the pressure of your body smashes up against the blood vessels that return to your ticker, but “sleeping on your left side with your right side not squished is supposed to potentially increase blood flow back to your heart.” And anything you can do to help your most important organ pump more efficiently is good for your health, he says.
Pregnant women, in particular, should consider sleeping on their left side because the baby is pushing their organs upward, says Winter. (There’s only so much space in there, after all!) During pregnancy, the heart is already working harder to support the baby, and snoozing on the right side, combined with the extra pressure from the organs, could hinder the flow of blood to mom’s heart — and to the little one, says Winter.
As for why sleeping on either side might be "bad," the CNN article said that it could cause "poor blood flow" and an increase in acid reflux and heartburn.
We showed Winter the ad, the Money Cougar article, and the CNN story. By email, he reiterated the information from the CNN story and referred to sleeping on the left side instead of the right as nothing more than a "tip."
He said: "This 'tip' stems from the fact that if you look at a diagram of typical human circulation, venous blood returns to the heart via the left-sided vena cava system, so sleeping on your right side theoretically could impede that return flow. This is most often cited with pregnant women as that extra weight could be a small issue. I sleep on my left side all of the time!"
More importantly, we asked him if he would say that the ad about him "warning" not to sleep on the right side was at least a little bit misleading and if he was simply offering some helpful advice about how the human body works. He answered: "That is absolutely correct. If someone asked which side to sleep on, all things considered, the left side might be better, but that research is very thin. I do not WARN people."
What Did Other Sleep Specialists Say?
Second, we contacted sleep medicine specialist Dr. Atul Malhotra, a professor of medicine at the University of California, San Diego, to ask about side sleeping.
Dr. Malhotra told us by email: "My bias is that sleep position (left vs. right) does not matter outside of [patients who experienced] heart failure." He linked us to a study that looked at whether patients with congestive heart failure should avoid sleeping on their left side. In other words, the avoidance of sleeping on one side or the other might only be truly advised to a small number of patients.
"Sleeping on the back can make things worse in sleep apnea and in this context, we would encourage sleeping on the side in people with documented sleep apnea," Dr. Malhotra said. "Most patients toss and turn so sleeping exclusively in one position is generally not achievable. In pregnancy, there is some controversy but some recommend avoiding supine sleep."
For a third opinion, we looked to an Associated Press article with quotes from Dr. Keith W. Roach, M.D., who is with Weill Cornell Medicine.
Dr. Roach appeared to provide data on the benefits of sleeping on the left or right side:
Most people can sleep in whatever position they find comfortable without any problem. However, there are a few instances in which sleeping on the left side may potentially cause problems. One is in people with untreated obstructive sleep apnea, in which several studies have shown that sleeping on the left side leads to slightly more breathing problems than sleeping on the right. However, in people who are treated, that should not be a problem.
Pregnant women should sleep on the side. Although women have often been recommended to sleep on their left side, either side is fine for the baby. Left-sided sleeping may reduce swelling in the feet.
People with known severe congestive heart failure or coronary artery disease and who habitually sleep on the left side have a small increase in death compared with back sleepers or right-side sleepers. However, my opinion is that the benefit is so small that comfort and quality of sleep is more important.
In sum, there might be different reasons as to why sleeping on the left or right side might be positive or negative, depending on their sleeping manner and any conditions they may or may not have. However, the opinions of these three medical professionals showed that there appeared to be no real impending danger to the population at large should they choose to sleep on the left or right side.
We advise any readers with questions about sleep and their health to speak with their primary care physician.