Effect of serum leptin levels on hypercapnic ventilatory response in obstructive sleep apnea

Background: Leptin levels have been reported to be higher in patients with obstructive sleep apnea (OSA) than in control subjects with matching age and body mass index (BMI). Although animal studies have shown that leptin augments hypercapnic ventilatory response (HCVR), the effect of leptin on HCVR has not been clarified in OSA. Objectives: To investigate whether leptin could augment HCVR during wakefulness in patients with OSA. Methods: Of 134 consecutive patients with OSA, 13 eucapnic and 16 hypercapnic patients with OSA, and 12 control subjects matched for sex, age, and BMI were selected. Fasting serum leptin levels were collected, and HCVR during wakefulness assessed by the slope between minute ventilation and end-tidal PCO2. Results: There was a significant positive relationship between serum leptin levels and HCVR in the group including control subjects and eucapnic patients with OSA (r = 0.42, p < 0.05). Subgroup analyses suggest that serum leptin levels and HCVR were significantly higher in eucapnic patients with OSA than in control subjects. On the other hand, hypercapnic patients had lower HCVR than eucapnic patients (p < 0.05), whereas serum leptin levels were similar between the two OSA subgroups. Conclusion: Leptin levels and HCVR are correlated as long as the eucapnic condition is maintained. We speculate that a stimulating effect of leptin on HCVR may be masked by the hypoventilation state. Copyright (c) 2007 S. Karger AG, Basel.