Nose or Mouth: The Route Your Airway Prefers at Night

Twelve healthy adults with normal nasal function were tested in a randomised, crossover sleep study comparing nasal versus oral breathing. While awake, the two routes made little difference to airway resistance. Asleep, the picture changed sharply: breathing through the mouth roughly doubled airway resistance compared with the nose, and obstructive breathing pauses became far more frequent, an average of around 43 events per hour during oral breathing versus about 1.5 during nasal breathing.

The design's strength is its crossover structure, each person acting as their own control, which rules out much individual variation. Its limits are size, just 12 participants, and scope: everyone had normal nasal resistance to begin with, so the findings say nothing about people whose nose is genuinely blocked, for whom mouth breathing may be doing useful compensatory work. For a healthy sleeper with clear nasal passages, though, it is a clean demonstration that the airway has a strong mechanical preference, and it isn't the mouth.