INFLUENCE OF GENDER ON WAKING GENIOGLOSSAL ELECTROMYOGRAM AND UPPER AIRWAY-RESISTANCE

Obstructive sleep apnea is generally recognized as more common in men than in women. This could relate to gender differences in either venti latory control mechanisms or the structure and function of the pharyng eal airway. Most studies suggest that women have a structurally smalle r pharyngeal airway than men, which would likely predispose rather tha n protect them from airway collapse. However, pharyngeal airway patenc y is actually a dynamic interaction between anatomy and pharyngeal mus cle activity. We therefore hypothesized that females may have increase d pharyngeal dilator muscle activity, thereby protecting them from air way collapse during sleep. To test this hypothesis, we compared geniog lossal EMC (CC-EMC, measured as a percentage of maximal muscle activit y) and upper airway resistance in 22 healthy subjects, 11 males and 31 females, during wakefulness. No significant difference in pharyngeal resistance could be found between the genders. However, inspiratory pe ak phasic and expiratory tonic GG-EMG activity were both significantly greater in females (CG-EMC peak phasic; 24.3 +/- 3.8 versus 13.1 +/- 4.5% of maximum, p < 0.02; GG-EMG tonic; 12.2 +/- 2.8 versus 4.7 +/- 1 .2% of maximum, p < 0.01). In addition, females demonstrated a signifi cant EMG response to inspiratory loading that was not observed in men. We conclude that women have, under basal conditions during wakefulnes s, augmented genioglossal muscle activity compared with men. To the ex tent that this augmented muscle activity is maintained across states, the female airway may be more stable and less collapsible.