Influence of sex and age on duration and frequency of sleep apnea events.

OBJECTIVES: Differences between men and women potentially provide insight into the regulation sleep apnea events. This study, therefore, examined how apnea frequency and duration varied according to age, sex, and sleep stage in a clinical population. DESIGN: NA SETTING: NA PATIENTS: Patients were 215 women and 215 men referred to a sleep disorders center with symptoms of obstructive sleep apnea and matched for BMI. Apnea events were compared across three age groups (18-39, 40-59, and 60-88 years) in stage 2 and in REM sleep. INTERVENTIONS: NA RESULTS: In stage 2 sleep, young and middle aged women were similar averaging 15 and 13 apnea events per hour respectively. Men had significantly more events averaging 27 and 30 events per hour for the corresponding age groups. The apnea frequency doubled from middle age to older women, and the sex difference narrowed between the older males and females to a non significant difference (26 events per hour for women versus 34 events per hour for men). Apnea duration was significantly longer in men than in women. Stage 2 apnea duration increased significantly with age for men (20.1, 21.5, 23.8 s) and women (16.7, 18.3, 20.6 s) across the three age groups. This also occurred in REM sleep in for men (22.8, 26.5, 29.8 s) and women (19.3, 22.4, 26.6 s). CONCLUSIONS: Duration did not demonstrate the marked "menopausal effect" that there was for apnea frequency. Female gender and younger age conferred benefit primarily by preventing airway collapse (reduced apnea frequency) with less of an effect on apnea duration, i.e., the ability to end the apnea. Compared to stage 2 sleep, REM sleep reduced the differences between men and women in apnea frequency. One explanation may be that differences in muscle tone of the upper airway account for the sex differences in apnea frequency.

Nasal patency and the effectiveness of nasal continuous positive air pressure in obstructive sleep apnea.

Nasal airway obstruction may exacerbate sleep apnea and is difficult to quantify on clinical examination. In this study, we examined the relationship among nasal patency, the frequency of sleep apnea events, and effective nasal continuous positive air pressures. Acoustic rhinometry was used as an objective measurement of nasal cross-sectional areas in 76 patients without nasal symptoms who underwent study with diagnostic polysomnography because of obstructive sleep apnea. Patients with persistent obstructive sleep apnea were titrated to nasal continuous positive air pressure in a split night study. All subjects had a mean apnea/hypopnea index of 28, and those with obstructive sleep apnea had a mean apnea/hypopnea index of 43. Mean cross-sectional areas 1 to 4 cm into the nose were 1.7, 1.1, 2.1, and 2.8 cm2, respectively (F = 39, p < 0.001). However, there was no correlation between the apnea/hypopnea index and the cross-sectional area at the four distances (r = 0.03, 0.06, 0.02, and 0.02, respectively, p = not significant). Correlations between nasal continuous positive air pressures and cross-sectional areas did not reveal a significant relationship at any of the four sites (r = 0.09, 0.07, -0.03, 0.00, respectively). Findings in patients with apnea were also compared with those in patients without apnea and significant differences were not found (F = 0.019, p = not significant). Although it would seem intuitive that increased nasal obstruction is associated with the severity of obstructive sleep apnea and difficulty with the use of nasal continuous positive air pressure, this study shows that nasal patency, as measured by acoustic rhinometry, does not correlate with the severity of obstructive sleep apnea, as determined by the apnea/hypopnea index or the effective nasal continuous positive air pressure.

The acute effects of nefazodone, trazodone and buspirone on sleep and sleep-related penile tumescence in normal subjects.

This study examined the effects of nefazodone, trazodone and buspirone on sleep and sleep-related penile tumescence. Trazodone is a sedating antidepressant without anticholinergic properties. Nefazodone is a new antidepressant that is a structural analogue of trazodone but is less sedating. Buspirone is a nonsedating, nonbenzodiazepine anxiolytic with antidepressant properties. Nefazodone was compared to trazodone and buspirone in a double-blind, placebo-controlled crossover study in 12 normal healthy males. Nefazodone increased rapid eye movement (REM) sleep, whereas trazodone and buspirone suppressed REM sleep. The drugs only minimally affected other sleep stages. Trazodone increased total tumescence time by delaying the onset of detumescence; nefazodone increased total tumescence time only insofar as it increased REM sleep; buspirone did not change total tumescence time when compared to placebo. The results support a growing body of data indicating that not all antidepressants suppress REM sleep. The results also are consistent with the interpretation of an earlier study showing that trazodone prolongs penile tumescence during sleep as a result of its alpha-adrenergic blocking properties that suppress detumescence. Nefazodone, with less alpha-adrenergic blocking activity, did not abnormally penile tumescence beyond REM sleep.

Diaphragmatic pressures: transvenous vs. direct phrenic nerve stimulation.

Diaphragmatic force, determined by stimulating the phrenic nerve while simultaneously measuring the pressures in a closed respiratory system, was assessed in five anesthetized dogs over a 5-h period to evaluate the inherent variability of this technique. Transdiaphragmatic pressure (Pdi) was measured at functional residual capacity during stimulation (120 Hz, 0.2-ms duration) of one phrenic nerve by either direct phrenic nerve stimulation (DPNS) or transvenous phrenic nerve stimulation (TPNS). An analysis of variance showed no significant (P greater than 0.50) change during the 5-h period. There was a significant correlation (r = 0.94, P less than 0.001) between Pdi obtained by TPNS and that obtained by DPNS. It is concluded that either DPNS or TPNS can be used to evaluate diaphragmatic strength over a 5-h period and that TPNS can be used in lieu of DPNS.