The relationship between excessive daytime sleepiness and metabolic syndrome in severe obstructive sleep apnea syndrome

BACKGROUND: Excessive daytime sleepiness (EDS), which is commonly considered a cardinal sign of obstructive sleep apnea (OSA), may lead to an increased rate of metabolic syndrome (MetS), and be an independent risk factor for cardiovascular morbidity and mortality. The aim of this cross-sectional study was to examine the role of EDS in MetS and its components by researching severe OSA patients. METHODS: The records of 175 consecutive patients who underwent standard polysomnography and diagnosed severe OSA were included. Subjective daytime sleepiness was assessed using the Epworth sleepiness scale (ESS). Fasting glucose, lipids, insulin and polysomnography parameters were measured. A metabolic score was counted as the total number of the positive diagnostic criteria of MetS for each subject, which indicated the level of metabolic disorder. RESULTS: The prevalence of central obesity, hypertriglyceridemia, low high density lipoprotein-cholesterol and MetS (78.2% vs 28.6%) was significantly higher among EDS group compared with control group. Compared with non-EDS patients, patients with EDS showed significantly higher metabolic score (3.22 ± 0.94 vs 1.96 ± 1.06). After adjustment for confounders, ESS score, log insulin and age significantly predicted the metabolic score (β = 0.567, P = 0.000; β = 0.197, P = 0.001 and β = 0.118, P = 0.048, respectively). CONCLUSION: EDS was independently correlated with the sum of metabolic components in severe OSA patients. Our study suggested that EDS might be a potentially useful clinical marker to identify patients with severe OSA at risk of MetS.