While a good night's sleep can boost everything from memory to heart health, it can also be disturbed by several variables—including your sleep position. While some problems are easily fixed, like swapping out a too-firm pillow or adding a humidifier to your room, finding the right way to sleep isn't as simple as asking your friends for recommendations. "One size does not fit all, and it depends on individual factors," says Dr. Charlene Gamaldo, medical director at the Johns Hopkins Sleep Disorders Center. "It's quite variable and depends on patient preference and the presence of other medical conditions or symptoms the patient may be experiencing." While new factors present themselves each and every night (given weather changes, mattress wear-out, and noise fluctuations), your preferred sleep position is likely rooted in childhood. According to a 2004 study published in The Internet Journal of Allied Health Sciences and Practice, researchers found that people have often established their preferred sleep positions as early as age seven.
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But your favorite position might not be serving you well, especially if you're now experiencing any health issues. Whether you're suffering from a temporary cold or chronic back pain, sleeping on your back, side, or stomach can exaggerate some conditions or help relieve others—and the position in which you doze may be affecting the quality of your rest (and how you feel the next day). Some patients with chronic back pain report a better night's sleep when they rest on their side with the aid of a body pillow, says Gamaldo, though it can depend on which side: Pregnant women and patients with heart failure aren't encouraged to sleep on their left side, and sleeping on the right may worsen acid reflux. (According to clinical sleep educator Terry Cralle, side sleeping is considered the most common position.)
Sleeping on your back, says Gamaldo, "may be more comfortable in case of nasal congestion or joint pain," but "less optimal" for patients who have acid reflux, trouble with snoring, or sleep apnea; it can also decrease the amount of toxins your brain is able to clear during sleep (side-sleeping is best for this, per a 2015 Stony Brook University study). And if you're a dedicated stomach sleeper, you could exacerbate spinal, back, nasal, or sinus issues—but you could also decrease the snoring habit that your partner can't stand.
Of course, most people don't just fall asleep on their backs and stay there. According to Cralle, adults change their sleeping positions many times during the night—sometimes up to 36 times total. "The number of position changes during sleep may be related to several factors including temperature, firmness of the sleep surface, health and medical conditions, bed partner movement, an uncomfortable mattress and/or pillow, noise, age, weight, an unfamiliar sleep environment, medications, and more," she says.
If you think your habitual sleep position may be making your 40 winks less rejuvenating than they should be, you can try a few simple ways to retrain your body. "It is possible to condition yourself with things like pillows or alerting devices that wake you slightly if you roll over," says Gamaldo, noting that these changes may position you for a better day ahead. Another pro tip? Consider investing in an adjustable bed, which will help you target the position best for you. "Sometimes you have to adjust the sleep surface to match your preferred sleep position rather than the other way around," Cralle says. "I am a big fan of adjustable bases (they are not just for the older crowd or for those with medical issues). They offer a lot more position and comfort options than lying flat on a sleep surface."
Additional reporting by Rebecca Norris.