Excessive daytime sleepiness (EDS), defined as an Epworth Sleepiness Scale (ESS) score >10, is an important symptom of obstructive sleep apnea (OSA) associated with increased cardiometabolic risk and motor vehicle or occupational accidents. The estimated prevalence of EDS in OSA patients ranges between 25 and 50%. We analyzed EDS-associated variables in OSA patients of the European Sleep Apnea Database (ESADA) cohort. Since a previous analysis had shown significant differences in EDS prevalence according to Countries, we explored the factors possibly associated to such variability by considering some lifestyle variables derived from data of the World Health Organization (WHO), and the reported prevalence of symptoms of depression. In 20,772 patients with suspected OSA (71% M, mean age 53.5±13.0 years, BMI 32.0±7.0 kg/m2, AHI median 21/h, range 5-49) EDS prevalence was 43%. Logistic regression identified the following factors accounting for only 2.5% of EDS variability: obesity, BPCO, severe OSA, sleep duration < 6 h/night, and severity of nocturnal hypoxemia, while age and presence of hypertension exerted a protective effect. EDS showed significant heterogeneity in  different Countries (men ESS score 9.21, 95% CI 8.69-9.73), and meta-regression using the data on obesity, sedentary lifestyle, alcohol use and prevalence of symptoms of depression in each Country showed a significant effect on EDS only for depression (p=0.04).  Therefore, differences in the prevalence of depression could at least partly explain the low predictivity for EDS of the factors identified by the logistic regression analysis.