Mechanism of Gastroesophageal Reflux in Obstructive Sleep Apnea: Airway Obstruction or Obesity?

Study Objectives: This is the first study to compare reflux events during wake and sleep in obese and non-obese individuals with obstructive sleep apnea (OSA) and obese individuals without OSA. The primary aim of the study was to investigate any additive effect of OSA on gastroesophageal reflux (GER) above that of obesity. Methods: Twenty obese individuals (body mass index, BMI > 30 kg/m(2)), 9 non-obese individuals (BMI < 30 kg/m(2)) with moderate-to-severe OSA, and 17 obese control subjects (BMI > 30 kg/m2) underwent high-resolution esophageal manometry, 24-h esophageal pH-impedance monitoring, and in-laboratory polysomnography. Results: Mean body mass index was 40 +/- 6 and 27 +/- 4 kg/m(2) for the obese and non-obese OSA groups, respectively, and 34 +/- 5 kg/m(2) for the obese control group. Apnea-hypopnea index (AHI) was 50 +/- 30 and 30 +/- 25 per hour for the obese and non-obese OSA groups (p > 0.05), significantly higher than that of the obese control group (3 +/- 3 per hour, p < 0.05). The two obese groups did not show any significant differences in the total number of acidic reflux events (41 +/- 20 vs 28 +/- 16); however, the obese OSA group had a greater number of acidic reflux events compared to the non-obese OSA group (22 +/- 12 events, p < 0.05). In multivariate analysis, BMI significantly predicted number of acidic reflux events (r(2) = 0.16, p = 0.01) during the 24-h period; however, AHI showed no significant association with any measure of GER severity. Conclusions: This study confirms an important role for obesity, rather than OSA per se in the relationship between OSA and GER.