Excellent question - and i would like to extend it if I may by asking if there is a proper way for people with shoulder / neck pain to sleep? I find if I lie on my affected side it is agony, on the other side it is almost as bad, and on my back it feels like I am lying on a boulder!
Conventional wisdom is to sleep on your back with a couple of pillows under your knees to reduce pressure on the back. or on yourside with the pilows between your knees.