Obstructive Sleep Apnea, dental health and overall well being

Obstructive Sleep Apnea (OSA) has detrimental effects on oral health (dental carries, gum recession) as well as overall health (Migraines, lethargy, cardio vascular disease, and possible depression/anxiety). Why is OSA so common? Is it a 21st century problem, or human genetics? What are possible cures, remedies or therapies other than the single, but trustworthy, CPAP machine?

From my own personal experience, Myofunctional Therapy has helped immensely, but falls shy of a "cure".