Purpose: Although excessive daytime sleepiness (EDS) is one of the key symptoms of obstructive sleep apnea (OSA), associations between OSA and EDS have been inconsistent, even in patients with severe OSA. To that end, our goal was to investigate factors associated with EDS based on the Epworth Sleepiness Scale (ESS) score in a large clinical population with severe OSA (apnea-hypopnea index ≥30).
Methods: This cross-sectional study included 1,126 consecutive adult patients referred for their first in-laboratory polysomnogram for suspicion of OSA. All patients completed a routine questionnaire including demographics, race, co-morbidities, sleep history, ESS, short-form quality of life questionnaire-12 (SF-12), the Center for Epidemiologic Studies Depression scale, and medications used. Severe OSA was diagnosed in 498 patients. After excluding patients taking narcotics, hypnotics, benzodiazepines, antidepressants, or those with diagnosis of depression, 355 patients remained in the final analytic cohort. Patients were divided into quartiles based on the ESS and comparisons were made between the lowest quartile (ESS ≤ 6; n = 105) and highest quartile (ESS ≥ 13; n = 97).
Results: Compared to the ESS ≤ 6 group, patients in the ESS ≥ 13 group had a significantly higher 3 % oxygen desaturation index and a significantly lower oxygen saturation nadir during sleep (p < 0.05). Moreover, patients with severe OSA in the highest quartile of ESS had higher depressive symptomatology.
Conclusions: In patients with severe OSA, intermittent hypoxemia and depressive symptoms are important contributing factors to EDS.