['Obesity is frequently associated with obstructive sleep apnea (OSA). Both conditions are proinflammatory and proposed to deteriorate cardiac function. We used a nested cohort study design to evaluate the long-term impact of bariatric surgery on OSA and how weight loss and OSA relate to inflammation and cardiac performance.', 'At 10-year follow-up in the Swedish Obese Subjects (SOS) study, we identified 19 obese subjects (BMI 31.2 ± 5.3 kg m(-2) ), who following bariatric surgery at SOS-baseline had displayed sustained weight losses (surgery group), and 20 obese controls (BMI 42.0 ± 6.2 kg m(-2) ), who during the same time-period had maintained stable weight (control group). All study participants underwent overnight polysomnography examination, echocardiography and analysis of inflammatory markers.', 'The surgery group displayed a lower apnea hypopnea index (AHI) (19.9 ± 21.5 vs. 37.8 ± 27.7 n/h, P = 0.013), lower inflammatory activity (hsCRP 2.3 ± 3.0 vs. 7.2 ± 5.0 mg L(-1) , P < 0.001), reduced left ventricular mass (165 ± 22 vs. 207 ± 22 g, P < 0.001) and superior left ventricular diastolic function (E/A ratio 1.24 ± 1.10 vs. 1.05 ± 0.20, P = 0.006) as compared with weight stable obese controls. In multiple regression analyses including all subjects (n = 39) and controlling for BMI, the AHI remained independently associated with hsCRP (β = 0.09, P < 0.001), TNF-α (β = 0.03, P = 0.031), IL-6 (β = 0.01, P = 0.007), IL 10 (β = -0.06; P = 0.018), left ventricular mass (β = 0.64, P < 0.001), left atrial area (β = 0.08, P = 0.002), pulmonary artery pressure (β = 0.08, P = 0.011) and E/Ea ratio (β = 0.04, P = 0.021).'] Does sleep apnea modify the long-term impact of surgically induced weight loss on cardiac function and inflammation?