How to evaluate excessive daytime sleepiness in Parkinson's disease

Excessive daytime sleepiness (EDS) is now recognized as an important problem in Parkinson's disease (PD), and its detection and treatment are clinically relevant. Several methods are available to evaluate EDS. Subjective methods consist of questionnaires to be filled out by the patient and include, among others, the Stanford Sleepiness Scale, the Karolinska Sleepiness Scale, and the Epworth Sleepiness Scale. These are entirely dependent on the patients' perception of their problems. Objective methods evaluate sleepiness indirectly, measuring the time it takes for the subject to fall asleep when placed in a soporific situation. Two types can be further identified: those using electrophysiologic measures [the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT)] and those measuring performance (e.g., the Oxford Sleep Resistance test). The Epworth Sleepiness Scale and the MSLT have been used repeatedly in PD and, in spite of their limitations, they are, together with the MWT, the best available methods to measure EDS in these patients.