There are many different interpretations on the significant of your sleep position. Many descriptions attribute personality traits to each of various sleep positions. Some allude to health issues in brief, but here’s a simple explanation for why you prefer to sleep on your back, side or stomach: Your ability to breathe properly.
As I describe extensively in my book, Sleep, Interrupted, most modern human’s jaws are smaller than what it was hundreds of years ago, and due to crowding of the airway, we’re all susceptible (to various degrees) to our tongues collapsing and obstructing our breathing, especially if we’re on our backs. The tongue, which grows to its’ normal size, takes up relatively too much space, and when lying on your back, falls back almost completely. The only thing that’s keeping you from obstructing is some muscle tension when you inhale.
The problem is when you go into deeper stages of sleep, where by definition, your muscles much relax. In REM sleep (the dreaming stage), all your muscles are relaxed completely, except for your eyes and diaphragm. This is when you’ll stop breathing, take a few breaths in against a closed throat, wake up and roll over. Most people with this issue know that they have to sleep only on their side or stomach is they want to sleep at all.
Problems occur if you’re suddenly forced to sleep on your back due to a shoulder or hip injury, or if you undergo an operation and are forced to sleep on your back. It’s not uncommon for someone to realize that all their problems started when they began to sleep on their backs.
This process also explains why sick people get even sicker in hospitals: They are forced to sleep on their backs. When I was a surgical intern, I noticed that relatively healthy people coming in for routine procedures had a much higher rate of heart attacks and pneumonias.
The American Academy of Dermatology recommends that women avoid sleeping on their side or stomach, to prevent facial wrinkles. Bad advice. I can’t tell you how many times patients who come in for sinus infections, fatigue, chronic cough, or headaches realize that all this began when they followed these recommendations. Not sleeping well can definitely aggravate more wrinkles.
So what’s the best sleep position? Ultimately, it’s what you’re most comfortable with. Of course, you can experiment and try different sleep positions. I had one acquaintance who was going through menopause and was in the habit of sleeping on her back. I told her to try sleeping on her side. One month later, she reported that she was sleeping significantly better. I think you’ll agree with me that the quality of your sleep can definitely affect your moods and personality.