Serum amyloid a and obstructive sleep apnea syndrome before and after surgically-induced weight loss in morbidly obese subjects

Background: Serum amyloid A (SAA) is an inflammatory marker associated with cardiovascular disease (CVD) and found to be increased in obesity. Obstructive sleep apnea (OSA) syndrome, a frequent complication of obesity also associated with CVD risk, is improved after surgically-induced weight loss. To explore the potential role of SAA in the relation between OSA and CVD, we investigated relationships between changes in SAA concentrations and nocturnal respiratory events in obese subjects undergoing bariatric surgery. Methods: We measured plasma SAA and used nocturnal respiratory polygraphy to assess the apnea-hypopnea index (AHI), the oxygen desaturation index (ODI) and the mean and lowest O-2 saturation (SaO(2)) in 61 morbidly obese patients before either adjustable gastric banding or gastric bypass. For 35 subjects with OSA, the same data were obtained 1 year after the surgery. Results: Before surgery, SAA concentrations were significantly higher in patients with severe OSA (56.2+/-6.4 mu g/ml) compared to subjects with moderate OSA (22.9+/-3.2 mu g/ml) or without OSA (16.2+/-2.2 mu g/ml). Plasma SAA correlated positively with AHI and ODI, and negatively with mean and lowest SaO(2). After surgery, plasma SAA decreased significantly by 41.7%, and changes in plasma SAA correlated with variations in OSA parameters. In multivariate analyses, AHI was a predictor of plasma SAA, independent of BMI, both at baseline and during weight loss. Conclusion: The improvement of OSA after bariatric surgery is associated with a decrease in SAA, independent of the change in BMI. SAA may represent a marker of the improvement in CVD risk profile after surgically-induced weight loss in patients with OSA.