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

Abstract

To examine whether circulating leptin levels correlate with the severity of disease in patients with obstructive sleep apnea. Prospective nonrandomized study. 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. Leptin levels (mean +/- SD) were 21.2 +/- 8.6, 16.2 +/- 5.2, and 10.6 +/- 7.5 ng/mL (P =.005) in patients 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). 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.