PLoS One 17 (5): e0268677, 2022. doi: 10.1371 / journal. pone.0268677 Etiology of Obstructive Sleep Apnea (OSA) Anatomic risk factors for obstructive sleep apnea include An oropharynx "crowded" by a short or retracted mandible A prominent tongue base or tonsils A rounded head shape and a short neck A neck circumference > 43 cm (> 17 in) Thick lateral pharyngeal walls and parapharyngeal fat pads Such risk factors may not predict severity.