title: Persistence of obstructive sleep apnea after surgical weight loss.
abstract: OBJECTIVE
  Weight loss may reduce the severity of obstructive sleep apnea (OSA), but persistence of OSA following surgical weight loss has not been defined. We sought to clarify the impact of bariatric surgery on OSA. We hypothesized that, despite substantial weight loss and reductions in the apnea-hypopnea index (AHI), many will have persistent disease.
  
  
  METHODS
  Consecutive patients referred for preoperative sleep evaluation underwent polysomnography before and 1 year following bariatric surgery. We compared the effects of weight loss on body mass, OSA, and continuous positive airway pressure requirements. We defined OSA severity using the AHI (normal < 5 events per hour, mild 5 to 14 events per hour, moderate 15 to 29 events per hour, and severe 30 or more events per hour). We identified predictors of OSA severity following weight loss and assessed compliance with therapy.
  
  
  RESULTS
  Twenty-four patients (aged 47.9 +/- 9.3 years; 75% women) were enrolled. At baseline, all subjects had OSA, the majority of which was severe. Weight loss reduced body mass index from 51.0 +/- 10.4 kg/m2 to 32.1 +/- 5.5 kg/m2 (p < 0.001) and the AHI from 47.9 +/- 33.8 to 24.5 +/- 18.1 events per hour (p < 0.001). At follow-up, only 1 patient (4%) experienced resolution of OSA. The majority (71%) had moderate or severe disease. The most important predictor of the follow-up AHI was the baseline AHI (R2 = 0.603). All patients with residual OSA required continuous positive airway pressure to ablate apneic events, but the required pressures decreased from 11.5 +/- 3.6 cm H2O to 8.4 +/- 2.1 cm H20 (p = 0.001). Only 6 patients were compliant with continuous positive airway pressure therapy at the follow-up visit.
  
  
  CONCLUSIONS
  Surgical weight loss reduces the AHI, but many patients have residual OSA one year after bariatric surgery.
authors.affiliation: Pulmonary, Critical Care and Sleep Medicine Service, Walter Reed Army Medical Center, Washington, DC 20307, USA. christopher.lettieri@us.army.mil
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Lettieri
authors.forename: Arn H
authors.initials: AH
authors.lastname: Eliasson
authors.forename: David L
authors.initials: DL
authors.lastname: Greenburg