The association of the severity of obstructive sleep apnea with plasma leptin levels

Objective: To examine whether circulating leptin levels correlate with the severity of disease in patients with obstructive sleep apnea. Design: Prospective nonrandomized study. Setting: Referral sleep laboratory for patients with sleep-disordered breathing and biochemistry laboratory. Patients: Thirty-two subjects (mean+/-SD age, 47+/-12 years) who were referred for suspected sleep apnea underwent an overnight sleep study and fasting morning venous blood sampling. Patients were divided into 3 groups with respect to apnea-hypopnea index: (1) severe sleep apnea (n=8), apnea-hypopnea index greater than 20; (2) mild sleep apnea (n=12), apnea-hypopnea index between 5 and 20; and (3) nonapneic control (n=12), apnea-hypopnea index less than 5. Results: Leptin levels (mean+/-SD) were 21.2+/-8.6, 16.2+/-5.2, and 10.6+/-7.5 ng/mL (P=.005) inpatients with severe and mild obstructive sleep apnea and nonapneic controls, respectively. Plasma leptin levels correlated positively with the degree of sleep-disordered breathing as recorded by the apnea-hypopnea index (r=0. 54, P=.001) and percentage of sleep time spent with oxygen saturation below 90% (r=0.39, P=.02). Conclusions: Circulating leptin concentrations in patients with obstructive sleep apnea, independent of body mass index and age, are significantly higher than levels in nonapneic controls and there is a positive relationship between leptin concentrations and the severity of sleep apnea. Hyperleptinemia may be a prognostic marker of obstructive sleep apnea syndrome.