Wow, I hadn't ever considered the skin aging effects of your sleeping position before.

http://dailyhealthpost.com/8-sleeping-positions-and-their-effects-on-health/

Relevant parts:
Quote:
sleeping on your back may also help to prevent facial wrinkles and skin breakouts.

When you’re sleeping on your side with both arms down, the spine is best supported in its natural curve. This can definitely help reduce back and neck pain while also reducing sleep apnea. The downside? Sleeping on the side can contribute to skin aging due to gravity, meaning facial wrinkles and sagging breasts.