Many people who present to massage therapists who are seen for muscle tension and spasms tend to have upper airway obstruction. This is what a recent article states on massagetoday.com. The article was co-written by a dentist, who has clearly has an advanced understanding of upper airway anatomy and physiology.
What they imply is that many patients who present to massage therapists for various neck/shoulder/back tension or soreness will have some degree of upper airway narrowing, which forces poor head posture, leading to a chain reaction involving other various muscle groups. All this comes from constricted jaw structures. People who have constricted breathing passageways tend to jut their head forward or tilt it back slightly. These maneuvers will open the space behind the tongue significantly. Using Contour pillows or a log-roll type pillow will also open up your airway.
The point of the article is that massage therapists can be the first line people who can pick up any significant sleep-breathing problems.