The effect of surgical and non-surgical weight loss on N-terminal pro-B-type natriuretic peptide and its relation to obstructive sleep apnea and pulmonary function

BACKGROUND: Obesity is a major risk factor for obstructive sleep apnea, impaired pulmonary function and heart failure, but obesity is also associated with paradoxically low levels of serum N-terminal pro-B-type natriuretic peptide (NT-proBNP). In subjects with severe obesity undergoing weight loss treatment, we assessed the associations between changes in severity of obstructive sleep apnea, pulmonary function and serum NT-proBNP levels. METHODS: One-year non-randomized controlled clinical trial. Participants, 69.6 % women, mean (SD) age 44.6 (10.8) years and body mass index (BMI) 45.1 (5.6) kg/m(2), underwent gastric bypass surgery (n = 76) or intensive lifestyle intervention (n = 63), resulting in 30 (8) % and 8 (9) % weight loss, respectively. The reference group included 30 normal weight, healthy, gender and age matched controls. Sleep recordings, arterial blood gases, pulmonary function and blood tests were assessed before and 1 year after the interventions. RESULTS: NT-proBNP concentrations increased significantly more after surgery than after lifestyle intervention. The post intervention values in both groups were significantly higher than in a normal weight healthy reference group. In the whole study population changes (∆) in NT-proBNP correlated significantly with changes in both BMI (r = -0.213) and apnea hypopnea index (AHI, r = -0.354). ∆NT-proBNP was, independent of age, gender and ∆BMI, associated with ∆AHI (beta -0.216, p = 0.021). ∆AHI was, independent of ∆BMI, significantly associated with changes in pO2 (beta -0.204), pCO2 (beta 0.199), forced vital capacity (beta -0.168) and forced expiratory volume first second (beta -0.160). CONCLUSIONS: Gastric bypass surgery was associated with a greater increase in NT-proBNP concentrations than non-surgical weight loss treatment. Reduced AHI was, independent of weight loss, associated with increased NT-proBNP levels and improved dynamic lung volumes and daytime blood gases. Clinical Trial Registration ClinicalTrials.gov NCT00273104, retrospectively registered Jan 5, 2006 (study start Dec 2005).