Several factors have been identified as predictors of sleepiness in persons with epilepsy using the Epworth Sleepiness Scale as a subjective measure of daytime sleepiness (Malow et al., 1997; Sanchez de Leon et al., 1997). The ESS is a self-administered, eight-item questionnaire designed to ascertain sleep propensity in a variety of everyday situations (Johns, 1992). The scale has been validated in a variety of situations, and was found to correlate with results of the MSLT, the gold standard for the objective measurement of daytime sleepiness (Chervin et al., 1997).
Excessive daytime sleepiness as measured by the ESS was found in 28% of 158 subjects with epilepsy and 18% of 68 control subjects with other neurologic disorders (Malow et al., 1997). Symptoms of sleep apnea and RLS reliably predicted daytime sleepiness. Having epilepsy conferred only a nonsignificant trend for EDS. Patients with epilepsy between the ages of 30 and 45 years were most likely to report daytime sleepiness. In patients with epilepsy, the number and type of AEDs, seizure frequency, epilepsy syndrome, and presence of sleep-related seizures were not significant predictors of daytime sleepiness.
At our institution, 82 consecutive patients admitted to the epilepsy monitoring unit completed sleep questionnaires, the ESS, and Beck Depression Inventory (BDI) (Beck, 1987; Foldvary et al., submitted for publication). An ESS score greater than 8 was considered elevated, suggesting the presence of daytime sleepiness (Johns, 1992). Of the 82 patients, 47% had an ESS greater than eight. Patients were taking a mean of 1.87 AEDs. The group had a mean BDI of 11, and 31% of patients had a score of 15 or higher suggesting symptoms of depression (Beck, 1987). Higher number of AEDs, elevated BDI, and the use of sleeping aids were predictive of daytime sleepiness. No correlation between the ESS and seizure frequency was found.
The causes of EDS in the epileptic population are multifactorial. AEDs, seizures, and concomitant sleep disorders have been found to affect sleep macroarchitecture and produce daytime sleepiness. Patients with epilepsy have a high incidence of sleep complaints and poor sleep habits. Primary sleep disorders should be suspected in patients with persistent hypersomnia, particularly those on AED monotherapy or with low serum drug concentrations and well-controlled seizures. Treatment of sleep disorders and improved sleep hygiene may lead to better seizure control.
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