Original articleEffects of gender on upper airway collapsibility and severity of obstructive sleep apnea
Introduction
Obstructive sleep apnea (OSA) is more common in men than women despite the fact that women with OSA tend to be more obese and have smaller upper airway size than men [1], [2], [3], [4]. This gender difference in the prevalence of OSA has not been adequately explained on the basis of obesity, upper airway size and neural control of upper airway muscles [5], [6], [7]. In a recent study by Pillar et al., men demonstrated more collapsibility of the upper airway during sleep than women when exposed to an external inspiratory load [8]. However, they found no gender difference in genioglossal or tensor palatini muscle activation in response to inspiratory resistive loading during sleep, suggesting differences in upper airway anatomy and mechanics rather than neural control of upper airway muscles. The current concept of the mechanism of upper airway maintenance during sleep suggests a complex interplay between intrinsic mechanical properties of the pharynx and neural regulation of pharyngeal dilator muscle activities. During sleep the neural inputs to pharyngeal dilator muscles are diminished, allowing the anatomical forces to increase pharyngeal collapsibility. Body position plays a significant role in the severity of OSA. Studies found that the number of obstructive events during sleep was much higher for the supine position than the lateral position in patients with OSA [9], [10]. The pharyngeal airway is structurally surrounded by soft tissues such as the tongue and lateral soft tissue. Watanabe and colleagues recently suggested that the balance between the size of soft tissue and the bony enclosure, such as the mandible, determines the closing pressure of the airway [11]. Gravitational force is considered to be one significant determinant of the closing pressure [11]. The larger mass of the soft tissues, such as the tongue, located anterior to the pharynx, can exert greater gravitational force on the anterior pharyngeal airway wall while the patient is in the supine position, whereas the relatively smaller amount of the soft tissues located laterally may exert less pressure onto the lateral pharyngeal airway wall while the patient in the lateral position [11]. The mandible tends to move inferiorly and posteriorly during sleep in the supine position [12], a movement associated with decreased pharyngeal diameter and an increase in upper airway resistance [13], [14]. We hypothesized that women might be protected from developing severe OSA because of the intrinsic stability of the pharynx and limited changes in upper airway caliber during inferior-posterior mandibular movement. The present study examines the relationship between changes in upper airway size and the severity and position-dependency of OSA in men and women.
Section snippets
Subjects
Among the consecutive patients referred to the sleep center for assessment, 71 patients were enrolled in the study after being diagnosed with OSA, as defined by a respiratory disturbance index (RDI, sum of apneas and hypopneas) ≥5 events per hour sleep. The current cohort is a subsample of a previously reported population that met the inclusion criteria for the present study [15]. Patients with a prior uvulopalatopharyngoplasty or clinically evident maxillofacial abnormalities such as
Results
The study population consisted of 53 men and 18 women, with mean ages of 52.0±1.5 and 48.6±3.2 years, respectively. The anthropometric data and respiratory indices are shown in Table 1. The men and women were obese with body mass indexes (BMI) of 33.5±0.7 and 39.5±3.0 kg m−2 (P=NS), respectively. The degree of daytime sleepiness, based on Epworth sleepiness scale, was comparable in men and women. Mean awake and minimum arterial oxygen saturations (SaO2) during sleep were also similar. However,
Discussion
The present study shows that: (1) OSA is more position-dependent in men than women; and (2) men have a greater reductions in upper airway dimensions with retrusive movement of the mandible than women and the worsening of sleep apnea in supine position appears, in part, be related to the degree of reduction in airway caliber with retrusive movement of the mandible.
Although there are lines of evidence to suggest the role of pharyngeal muscle tone, airway compliance and anatomic variables in
Acknowledgements
The author thanks Lauren Pollio and Wendy Stegina for their valuable technical assistance. The author has no financial relationship with the equipment manufacturers mentioned in this study. This research was supported, in part, by the departmental fund from the Yale University School of Medicine.
References (36)
- et al.
Mandibular posture during sleep in patients with obstructive sleep apnoea
Arch Oral Biol
(1999) - et al.
Neural and anatomic factors related to upper airway occlusion during sleep
Med Clin North Am
(1985) Gender differences in the expression of sleep-disordered breathing: role of upper airway dimensions
Chest
(2001)- et al.
Quality of life in patients with obstructive sleep apnea: effect of nasal continuous positive airway pressure – a prospective study
Chest
(1999) - et al.
Flextube reflectometry for determination of sites of upper airway narrowing in sleeping obstructive sleep apnoea patients
Respir Med
(2001) - et al.
Treatment success with a mandibular advancement device is related to supine-dependent sleep apnea
Chest
(1998) - et al.
The occurrence of sleep disordered breathing among middle-aged adults
N Engl J Med
(1993) - et al.
Estimation of the clinically diagnosed proportion of sleep apnea syndrome in middle-aged men and women
Sleep
(1997) - et al.
Pharyngeal size in snorers, non-snorers, and patients with obstructive sleep apnea
N Engl J Med
(1986) - et al.
Anatomy of pharynx in patients with obstructive sleep apnea and in normal subjects
J Appl Physiol
(1997)
Pharyngeal cross-sectional area in normal men and women
J Appl Physiol
The effect of age, sex, obesity and posture on upper airway size
Eur Respir J
Pharyngeal cross-sectional area and pharyngeal compliance in normal males and females
Respiration
Airway mechanics and ventilation in response to resistive loading during sleep
Am J Respir Crit Care Med
Effect of sleep position on sleep apnea severity
Sleep
The effect of posture on upper airway dimensions in normal subjects and in patients with the sleep/hypopnea syndrome
Am Rev Respir Dis
Contribution of body habitus and craniofacial characteristics to segmental closing pressures of passive pharynx in patients with sleep disordered breathing
Am J Respir Crit Care Med
Effects of mouth opening on upper airway collapsibility in normal sleeping subjects
Am J Respir Crit Care Med
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2020, Sleep Medicine ReviewsCitation Excerpt :Notably, consistent evidence show that OSA is more common in men than women in the general population with a male-to-female ratio of approximately 1.5:1 [9,11,108,109]. Anatomical and physiological differences such as upper airway stability, ventilatory response to chemical stimuli or higher abdominal or neck fat, make men more susceptible to OSA [110–114]. The sex differences in prevalence also remains in older adults [9,115] though the prevalence of OSA seems to be higher in post-versus premenopausal women [116], somewhat suggesting that hormonal-related effects may be important in OSA pathogenesis in women.