Characteristics of obstructive sleep apnea in myasthenia gravis patients: a single center study.

Recent studies have shown a high prevalence of obstructive sleep apnea in myasthenia gravis compared to the normal population. The aim of this study was to elucidate clinical and polysomnographic differences between clinically stable Korean MG patients with and without OSA.A total of 18 consecutively stable MG patients were included in this prospective study. We compared MG patients with OSA (n = 7) and without OSA (n = 11) with respect to the baseline characteristics and overnight polysomnography (PSG) parameters. Demographic parameters, prescribed medication status, thymectomy status, myasthenia gravis foundation of America score, and antibody status were obtained from their medical records. We performed the Korean version of Pittsburg sleep quality index to assess the subjective quality of sleep. Statistical analyses were performed using SPSS version 18.0 with Wilcoxon rank sum test, chi-square test, Fisher's exact test, and Spearman correlation test.Among the clinical parameters, MG patients with OSA showed a higher proportion of male sex (p = 0.016) and increased body mass index (p = 0.033). The PSG showed an 11-fold higher supine apnea-hyponea index (AHI) in MG patients with OSA. AHI was further analyzed with supine and non-supine position. MG patients with OSA had a higher supine AHI (19.5 ± 15.8) compared to those without OSA (1.9 ± 1.2, P = 0.008). Most of MG patients with OSA (85.7%) showed more than two times higher supine AHI than non-supine AHI.This study showed that the occurrence of OSA in patients with MG is associated with male sex and obesity, which is in accordance with the normal population. Moreover, PSG data showed a high prevalence of supine dominant OSA in MG patients with OSA.