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) 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).
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.