Positional and Nonpositional Obstructive Sleep Apnea

Abstract

Background: Many patients with obstructive sleep apnea have a significant worsening of apnea in the supine position. The aim of this study was to describe the impact of body position on the clinical and polysomnographic data of OSA patients. Methods: A total of 765 consecutive OSA patients were diagnosed in our sleep center from March 2002 to December 2004. Among these, 512 patients who met the following criteria were recruited into this study: apnea hypopnea index (AHI)＞10, age＞20, and normally sleeping in either the supine, intermediate or lateral position for more than 30 minutes. We classified the subjects into a positional patients (PP) group (Supine AHI/Lateral AHI≥2) and a nonpositional patients (NPP) group (Supine AHI/Lateral AHI＜2). Anthropomorphic data, overnight polysomnography, and Epworth Sleepiness Scale (ESS) scores were collected for analysis. Results: Among the 512 subjects, 74% were positional patients and predominately male. Weight, body mass index (BMI), and neck circumference were significantly higher in the NPP group. Average weight in the NPP group was 8.8 kg heavier than in the PP group. ESS scores were also higher in the NPP group. The PP group tended to have a longer total sleep time and lower arousal index compared to the NPP group. The AHI and average apnea-hypopnea duration were significantly higher, and the average or minimal oxygen saturation was significantly lower in the NPP group. Using multiple logistic regression analysis, we found that the AHI, followed by the BMI and ESS scores, were strong predictive factors for the risk of developing positional OSA. Conclusion: This study demonstrated that the majority of OSA patients were positional- dependent. These positional-dependent patients were thinner and had a lower severity of AHI and daytime sleepiness. The AHI is the most dominant variable predicting positional dependency. Body weight reduction and positional therapy are important strategies, in addition to nasal CPAP, in the treatment plan for OSA patients.