Someone forwarded an article to me about the "best" and "worst" sleep positions. The article said that sleeping on your back is best and on your stomach is worst. They stated the "pros" and "cons" of all three positions, most of which I agree with. Of note, most of us change positions a few times each night, whether you remember it or not.
Sleeping on your back can reduce neck and back pain for some. If your head is elevated, back sleeping can decrease acid reflux disease. In theory, back sleeping could reduce wrinkles because gravity pulls your face skin onto your skull. The article also said back sleeping can be more supportive to your breasts, which could reduce breast sagging.
Side sleeping can also help some with neck and back pain, as well as reduce snoring. However, it can increase wrinkles and breast sagging because of the effect of gravity. Also, side sleeping is good for pregnancy, especially in the 2nd and 3rd trimesters.
Finally, stomach sleeping can further reduce snoring, but can exacerbate neck and back pain as the spine is not supported in this position.