Surely enough, positional therapy for OSA has been in practice for many years. Although prone position helps to reduce gravity effects and collapsability of the upper airway, I am not sure if detailed studies have been carried out.

We have more questions than answers:

Is prone is better than lateral? Is it good for all age group? Do we have adequate sample size? is there any controlled studies?

According to Menon and Kumar (2013), "Published data concerning adults in prone position are limited and not consistent. Further study of prone position in adults is needed".

Please refer their paper here:

http://www.hindawi.com/journals/isrn.otolaryngology/2013/670381/