GENDER DIFFERENCES IN AIRWAY-RESISTANCE DURING SLEEP

At the onset of non-rapid-eye-movement (NREM) sleep there is a fall in ventilation and an increase in upper airway resistance (UAR). In heal thy men there is a progressive increase in UAR as NREM sleep deepens. This study compared the pattern of change in UAR and ventilation in 14 men and 14 women (aged 18-25 yr) both during sleep onset and over the NREM phase of a sleep cycle (from wakefulness to slow-wave sleep). Du ring sleep onset, fluctuations between electroencephalographic alpha a nd theta activity were associated with mean alterations in inspiratory minute ventilation and UAR of between 1 and 4.5 l/min and between 0.7 0 and 5.0 cmH(2)O.1(-1).s, respectively, with no significant effect of gender on either change (P > 0.05). During NREM sleep, however, the i ncrement in UAR was larger in men than in women (P < 0.01), such that the mean levels of UAR at peak flow reached during slow-wave sleep wer e similar to 25 and 10 cmH(2)O.l(-1).s in men and women, respectively. We speculate that the greater increase in UAR in healthy young men ma y represent a gender-related susceptibility to sleep-disordered breath ing that, in conjunction with other predisposing factors, may contribu te to the development of obstructive sleep apnea.