[Excessive diurnal somnolence--causes, mechanisms, therapeutical approach].

Excessive diurnal somnolence (EDS) represents the major symptom of sleep apnea syndrome (SAS). It is mainly determined by sleep fragmentation due to repetitive arousals following the episodes of nocturnal apneas and it is aggravated by the associated hypoxemia/hypercapnia. The EDS related decreased vigilance has 3 types of consequences: psychological (decreased capability of attention and concentration, increased of the response time to stimuli, irritability), motor (physical performance impairment, automatic behaviour) and social (accidents, decreased working performance). EDS evaluation relies on non-instrumental and instrumental strategies which are comprehensively presented. The therapy of EDS implies causes recognition and treatment, optimization of sleep hygiene and psychological advise.