Insulin Resistance and Leptin Levels in Patients with Obstructive Sleep Apnea

Background and Objective: Obstructive sleep apnea (OSA) has been associated with metabolic syndrome, diabe-tes mellitus, and cardiovascular diseases. Insulin resistance and increased leptin levels could explain the impaired meta-bolic conditions in patients with OSA. This study aimed to assess the association of OSA severity with insulin re-sistance and leptin levels in a group of patients referred to a sleep disorders’ clinic. Materials and Methods: Seventeen patients without OSA and 28, 33, and 30 patients with mild, moderate, and se-vere OSA; respectively, were included in this study. All participants underwent full night polysomnography (PSG), and blood samples were collected in the morning after PSG. The insulin resistance index was estimated by homeostasis model assessment (HOMA). Results: HOMA values were not significantly different among the study groups. Significant difference in leptin lev-el was found between patients with severe and mild OSA. Leptin level was significantly correlated with age (r = 33, P = 0.020), apnea–hypopnea index (AHI) (r = 0.41, P = 0.004), and oxygen desaturation index (r = 46, P = 0.030). HOMA was insignificant positive correlation only with triglyceride level (P = 0.010). Stepwise multiple regression analysis showed that AHI, body mass index, and gender were determinants of leptin levels, however, no variable was found for predicting HOMA. Conclusions: Present findings suggest that leptin levels might be independently associated with severity of OSA. Other factors other than insulin resistance should be considered for increasing vascular diseases in patients with OSA.