Effects of surgical weight loss for treating obstructive sleep apnea

Weight loss has been reported to reduce the severity of obstructive sleep apnea (OSA), particularly in the obese population. However, prospective studies with polysomnography (PSG) for the precise evaluation of OSA are lacking especially in Asian countries. We evaluated the effects of surgical weight loss for treating OSA using PSG data obtained before and after surgery. We performed a prospective study analyzing the clinical and PSG data obtained from our cohort of bariatric surgical candidates with moderate to severe OSA, as confirmed by preoperative PSG. The patients underwent follow-up PSG at least 12 months after bariatric surgery (laparoscopic Roux-en-Y gastric bypass). Of the 47 patients (70.1 %) with moderate to severe OSA among 67 patients who underwent preoperative PSG, 10 patients underwent postoperative PSG. The mean apnea-hypopnea index (AHI) of these 10 patients significantly reduced from 51.0 +/- 34.2 to 9.3 +/- 12.9 events/h, while their mean body mass index (BMI) loss was from 39.9 +/- 8.3 to 26.9 +/- 4.4 kg/m(2). Although the severity of OSA improved considerably, OSA resolution was achieved in only five patients (50 %). When compared to the patients who achieved OSA resolution, the patients with residual OSA showed a tendency to have lower minimum arterial oxygen saturation (SaO(2)) levels and higher supine AHI values in preoperative PSG. Surgical weight loss resulted in the significant improvement of OSA associated with obesity. However, OSA remained in a considerable proportion of patients even after substantial weight loss. We recommend that postoperative PSG be considered for the evaluation of residual OSA, especially in patients with low minimum SaO(2) levels and high supine AHI in preoperative PSG.