Daytime sleepiness in patients with obstructive sleep apnoea syndrome and its correlation to insulin resistance

Introduction: Obstructive Sleep Apnoea Syndrome (OSA) is a highly prevalent sleep disorder characterized by recurrent airflow obstruction. OSA leads to chronic intermittent hypoxia and sleep fragmentation; thus provoking multiple metabolic derangements. The relationship between obesity resistance in patients with OSA is rather complex. Aim of the study: Our study attempted to reveal a connection between excessive daytime sleepiness (EDS) in OSA and insulin resistance by the means of homeostatic assessment of b-cell function (HOMA-IR). Materials and methods: We studied a population of 19 OSA patients with EDS, 19 OSA patients without EDS and 20 healthy non-OSA individuals closely matched. Both patients and controls had undergone full night polysomnography. All blood samples were obtained at 6PM in the morning after the night study and were used for the measurement of insulin. Daytime sleepiness was assessed and quantified by the Epworth Sleepiness Scale (ESS). Excessive daytime sleepiness is defined as ESS score>10. Results: There were no significant differences in HOMA-IR index values between the two groups of patients suffering from OSA who had EDS and those who did not have EDS (5.50±2.49 vs. 2.94±0.73 p=0.349). Conclusions: Our study shows that in patients with OSA the excessive daytime sleepiness is not a discriminative characteristic of those who have already developed insulin resistance. Therefore, daytime symptoms in patients with a diagnosis of OSA do not help in the identification of those at risk of metabolic syndrome.