Daytime sleepiness and polysomnographic variables in sleep apnoea patients

¹ Servei de Pneumologia Hospital Univ. Arnau de Vilanova, IRBLleida, Lleida, Catalunya, Spain
² Serveis de Pneumologia and Anàlisis Cliniques, Hospital Univ. Son Dureta, IUNICS, Fundació Caubet-Cimera, Palma de Mallorca, Spain
³ Division of paediatric Sleep Medicine, University of Louisville, Kentucky, USA

^* To whom correspondence should be addressed. E-mail: fbarbe{at}arnau.scs.es.

	Abstract

Excessive daytime sleepiness (EDS) is not invariably present in patients with obstructive sleep apnoea (OSAS). This study investigates polysomnographic determinants of EDS in patients with OSAS.

EDS was assessed using the Epworth Sleepiness Scale and the Multiple Sleep Latency Test (MSLT). Patients had EDS whenever the ESS was >10 and the MSLT <5 min. Absence of EDS was defined when ESS was <10 and the MSLT >10 min.

We studied 23 male patients with EDS (mean [±SD] Epworth 17±3 and MSLT 4±1 min) and 17 without EDS (Epworth 5±2 and MSLT 16±3 min). Both groups had similar apnoea-hypopnoea index (62±18 vs 60±20 h-1). Patients with EDS exhibited shorter sleep latency (11±16 vs 18±18 min., p=0.05) and a greater sleep efficiency (90±7 vs. 82±13%, p<0.05) than those without it. Patients with EDS showed lower oxygenation (lowest SaO2 69±12 vs 79±8%, p<0.01; mean SaO2 87±6 vs 90±5%, p<0.05). Sleep stage distribution and arousal index were not different between groups.

Patients with OSAS and EDS are characterized by shorter sleep latency, increased sleep efficiency and worse nocturnal oxygenation than those without EDS. Nocturnal hypoxemia can be a major determinant of EDS in patients with OSAS.

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