Treating OSA: Current and emerging therapies beyond CPAP : Non-CPAP therapies for the treatment of OSA

Obstructive sleep apnea is associated with an increased risk of cardiovascular events; whether treatment with continuous positive airway pressure (CPAP) prevents major cardiovascular events is uncertain.

To estimate the prevalence of Obstructive Sleep Apnea Syndrome (OSAS), using current clinical and epidemiological techniques, among the adult population of Sao Paulo, Brazil. This population-based survey used a probabilistic three-stage cluster sample of Sao Paulo inhabitants to represent the population according to gender, age (20-80 years), and socio-economic status. Face-to-face interviews and in-lab full-night polysomnographies using a nasal cannula were performed. The prevalence of OSAS was determined according to the criteria of the most recent International Classification of Sleep Disorders (ICDS-2) from American Academy of Sleep Medicine (2005). A total of 1042 volunteers underwent polysomnography (refusal rate=5.4%). The mean age+/-SD was 42+/-14 years; 55% were women and 60% had a body mass index>25 kg/m(2). OSAS was observed in 32.8% of the participants (95% CI, 29.6-36.3). A multivariate logistic regression model identified several independent and strong associations for the presence of OSAS: men had greater association than women (OR=4.1; 95% CI, 2.9-5.8; P<0.001) and obese individuals (OR=10.5; 95% CI, 7.1-15.7; P<0.001) than individuals of normal weight. The adjusted association factor increased with age, reaching OR=34.5 (95% CI, 18.5-64.2; P<0.001) for 60-80 year olds when compared to the 20-29 year old group. Low socio-economic status was a protective factor for men (OR=0.4), but was an associated factor for women (OR=2.4). Self-reported menopause explained this increased association (age adjusted OR=2.1; 95% CI, 1.4-3.9; P<0.001), and it was more frequent in the lowest class (43.1%) than either middle class (26.1%) or upper class (27.8%) women. This study is the first apnea survey of a large metropolitan area in South America identifying a higher prevalence of OSAS than found in other epidemiological studies. This can be explained by the use of the probabilistic sampling process achieving a very low polysomnography refusal rate, the use of current techniques and clinical criteria, inclusion of older groups, and the higher prevalence of obesity in the studied population. Copyright 2010 Elsevier B.V. All rights reserved.

The pathophysiologic causes of obstructive sleep apnea (OSA) likely vary among patients but have not been well characterized. To define carefully the proportion of key anatomic and nonanatomic contributions in a relatively large cohort of patients with OSA and control subjects to identify pathophysiologic targets for future novel therapies for OSA. Seventy-five men and women with and without OSA aged 20-65 years were studied on three separate nights. Initially, the apnea-hypopnea index was determined by polysomnography followed by determination of anatomic (passive critical closing pressure of the upper airway [Pcrit]) and nonanatomic (genioglossus muscle responsiveness, arousal threshold, and respiratory control stability; loop gain) contributions to OSA. Pathophysiologic traits varied substantially among participants. A total of 36% of patients with OSA had minimal genioglossus muscle responsiveness during sleep, 37% had a low arousal threshold, and 36% had high loop gain. A total of 28% had multiple nonanatomic features. Although overall the upper airway was more collapsible in patients with OSA (Pcrit, 0.3 [-1.5 to 1.9] vs. -6.2 [-12.4 to -3.6] cm H2O; P <0.01), 19% had a relatively noncollapsible upper airway similar to many of the control subjects (Pcrit, -2 to -5 cm H2O). In these patients, loop gain was almost twice as high as patients with a Pcrit greater than -2 cm H2O (-5.9 [-8.8 to -4.5] vs. -3.2 [-4.8 to -2.4] dimensionless; P = 0.01). A three-point scale for weighting the relative contribution of the traits is proposed. It suggests that nonanatomic features play an important role in 56% of patients with OSA. This study confirms that OSA is a heterogeneous disorder. Although Pcrit-anatomy is an important determinant, abnormalities in nonanatomic traits are also present in most patients with OSA.