Elucidating Predictors of Obesity Hypoventilation Syndrome in a Large Bariatric Surgery Cohort.

Although understanding predictors of obesity hypoventilation syndrome (OHS), a condition associated with increased morbidity and mortality, is of key importance for risk prediction, existing characterization is limited. We hypothesize that OHS patients referred for bariatric surgery have more severe obstructive sleep apnea and metabolic derangements compared with their eucapnic counterparts. A total of 1,718 patients undergoing polysomnography with end-tidal CO monitoring prior to bariatric surgery at Cleveland Clinic from September 2011 to September 2018 were included. OHS was defined by body mass index (BMI) ≥ 30 kg/m and either polysomnography-based end-tidal CO ≥ 45 mm Hg or serum bicarbonate levels ≥ 27 mEq/L based on the updated European Respiratory Society guidelines. Unadjusted and multivariable logistic regression models (odds ratio; 95% confidence interval) were used to examine OHS predictors consisting of factors in domains of patient characteristics, polysomnography (cardiorespiratory and sleep architecture), laboratory, and metabolic parameters. The analytic sample comprised 1,718 patients with the following characteristics: age of 45.3 ± 12.1 years, 20.7% were male, BMI = 48.6 ± 9 kg/m, and 63.6% were white individuals. OHS prevalence was 68.4%. Unadjusted analyses revealed a 1.5% increased odds of OHS (1.01; 1.00-1.03) per 1-unit BMI increase, 1.7% (1.02; 1.01-1.02) per 1% increase in sleep time Sa < 90%, 12% increase (1.12; 1.03-1.22) per 1-U increase in hemoglobin A1c, and 3.4% increased odds (1.03; 1.02-1.05) per 5-U increase in apnea-hypopnea index. The association of apnea-hypopnea index with OHS persisted after adjustment for age, sex, race, and BMI and its comorbidities (1.02; 1.01-1.04). OHS was highly prevalent in patients referred for bariatric surgery by more than two-thirds. Even after consideration of confounders including obesity, obstructive sleep apnea remained a strong OHS predictor, as were increasing age, male sex, nocturnal hypoxia, and impaired long-term glucose control. These findings can inform OHS risk stratification in bariatric surgery and set the stage for experimental studies to examine sleep-related respiratory and metabolic contributions to hypoventilation.