Background: Excessive daytime sleepiness (EDS) is a major but not universally present feature of obstructive sleep apnea syndrome (OSAS). The latter has been associated with glucose dysmetabolism and insulin resistance. The aim of this study was to examine the role of EDS by investigating potential differences between somnolent and non-somnolent OSAS patients in glucose metabolism, insulin resistance, and levels of cardiovascular risk factors.
Methods: Included were 25 newly diagnosed otherwise healthy OSAS patients, reporting EDS (ESS ≥ 11) and 25 age- and BMI-matched, non-somnolent (ESS ≤ 10) OSAS patients, who served as controls. Fasting glucose and insulin levels, as well as homeostatic model assessment of insulin resistance (HOMA(IR)) index, levels of hs-CRP, and lipidemic profile were measured.
Results: The two groups did not differ in anthropometric or sleep characteristics. A significant correlation of ESS with glucose (p = 0.004), insulin (p = 0.011), and HOMA(IR) (p = 0.031) was observed. Somnolent patients had higher levels of glucose (p = 0.045), insulin (p = 0.012), and HOMA(IR) (p = 0.027). No difference was detected in other markers between the two groups.
Conclusions: Daytime sleepiness in OSAS patients is associated with hyperglycemia and hyperinsulinemia. These results suggest its potential use as a surrogate marker of insulin resistance in such patients.