I used to sleep on my belly, but now, I often get creases from the pillow or whatever that sometimes take 5-6 hours to clear up!!! UGLY!!! So, I'm now sleeping on my back, took quite awhile to get used to it. Also, when I sleep on my stomach, I sometimes get puffy upper-eyelids (not lower) in the morning, especially if ate a bit too much salt the day before (that takes 1-2 hours to clear).
All of this is probably due to old age...