Excessive Daytime Sleepiness and Sleep Disorders in a Population of Patients with Epilepsy: a Case-Control Study

There are several primary causes for excessive daytime sleepiness (EDS) and sleep disorders in patients with epilepsy. Up to now, studies in the literature report conflicting data in terms of both prevalence and aetiology. The aim of our study was therefore to evaluate the prevalence of EDS and some sleep disorders in a population of patients with epilepsy treated with no more than two antiepileptic drugs (AEDs). We also investigated the role of the depression of mood as a variable that can negatively affect EDS.

We prospectively and consecutively recruited 99 patients with a diagnosis of epilepsy, sleep disorders and EDS, belonging to the Centre for Epilepsy of the Department of Experimental Biomedicine and Clinical Neurosciences of the University of Palermo. 61.6% of patients recruited were suffering from focal epilepsy, and 38.3% from generalized epilepsy. 68.6% were undertaking monotherapy and 27.2% were drug resistant. Patients were matched for sex and age (+/- 5 years) with 96 non epileptic controls recruited from high school students, college students, relatives and friends of the medical team that conducted the study. EDS was found in 11.1% of patients with epilepsy. Clinical evaluation of sleep disorders was performed using validated questionnaires to investigate excessive daytime sleepiness (EDS), insomnia, Restless Legs Syndrome (RLS) and Obstructive Sleep Apnoea Syndrome (OSAS). In a second phase of the study, 43 of the investigated patients and 34 controls - after giving their consent - underwent a polysomnographic examination by "Compumedics Somtè".

Our study shows a statistically significant difference between cases and controls with regard to the prevalence of RLS (p = 0.022) and severity of OSAS with an increased risk in moderate-severe forms of epilepsy (odd ratio [OR] 2.5) most significantly associated with male gender (p = 0.04) and focal epilepsy (OR 3.8) with PSG seizures (0.02). Moreover, a statistically significant difference was demonstrated about mood disorders (p = 0.001) among patients with epilepsy and non epileptic controls. Sleepiness in patients with epilepsy seems to be particularly related to both the depression of mood (p = 0.01) and the presence of OSAS (p = 0.03), as well as to a higher mean age (p = 0.006) and a longer duration of illness (p = 0.04).

Our results confirm that drowsiness trouble frequently complained by patients with epilepsy, is particularly related not only to the presence of OSAS but also to the depression of mood.