Objective: Obstructive sleep apnea (OSA) is associated with obesity, sympathetic activation, systemic inflammation, and cardiovascular morbidity. Obesity, beta-adrenergic agonists, and inflammation are linked to decreased expression and/or secretion of an adipose tissue-derived antiatherogenic hormone, adiponectin. The purpose of the study was to investigate whether OSA affected plasma levels of adiponectin, which might help explain OSA-associated cardiovascular morbidity.
Research methods and procedures: We randomly selected 68 otherwise healthy male subjects, either with moderate/severe OSA [apnea-hypopnea index (AHI)>or=20; n=35] or without OSA (AHI<or=5; n=33). The diagnosis of OSA was made based on prospective full polysomnography. Adiponectin was measured before polysomnography between 8 and 10 pm.
Results: AHI was higher in the OSA group (49.5+/-4.4 vs. 2.9+/-0.4 events/h; p<0.001). OSA subjects were also more obese, with greater BMI (33+/-1 vs. 30+/-1; p=0.016) and percentage body fat (29+/-1% vs. 26+/-1%; p=0.030). Adiponectin levels were 7.67+/-0.73 and 6.33+/-0.51 microg/mL in the OSA and non-OSA groups, respectively, and this difference was significant in covariate analysis (taking into account age, hemodynamic characteristics, measures of body fat, and OSA severity) (p=0.009). After excluding from both groups the subjects with extreme BMI, such that the OSA and non-OSA study cohorts had similar BMI and percentage body fat, subjects with OSA had significantly higher plasma adiponectin (8.49+/-0.92 vs. 6.32+/-0.55 microg/mL; p=0.042), differences also evident in covariate analysis (p=0.017).
Discussion: Plasma adiponectin levels are elevated in otherwise healthy subjects with OSA. Therefore, low adiponectin is unlikely to explain the association between OSA and cardiovascular disease.