Ma MA, et al. – This report focused on the effects of obstructive sleep apnea (OSA) severity, sex, and race on oropharyngeal airway length (OPAL) dimensions. Investigations suggested that sex–based reductions in epiglottis cross–sectional area (CSA) and increased OPAL in OSA subjects might enhance airway–collapse vulnerability, more so with greater disease severity, and partially underlie male vs female susceptibility to the sleep disorder.