Daytime sleepiness may be an independent symptom unrelated to sleep quality in Parkinson’s disease

Excessive daytime sleepiness (EDS) may represent a disabling non-motor symptom in patients affected by Parkinson's disease (PD). This is a secondary analysis of a previous study documenting the improvement of nocturnal sleep in PD patients treated by rotigotine vs placebo. Here we tested the supposition that EDS may represent a distinct PD non-motor symptom occurring independently of other sleep-wake disorders; moreover, we verified whether EDS can be influenced by the improvement of nocturnal sleep in PD. In the present study, we evaluated the daytime sleepiness of PD patients treated with nocturnal administration of rotigotine (PD-Rot) vs placebo (PD-Pla), as measured by both subjective (Epworth Sleepiness Scale-ESS) and objective (Multiple Sleep Latency Test-MSLT) tools. We included 21 PD-Rot compared to 21 PD-Pla patients and documented no significant changes of both ESS and MSLT data between baseline and follow-up visits in both groups. Moreover, we found no correlations between nocturnal sleep improvement and diurnal sleepiness. Therefore, these data suggest that the improvement of nocturnal sleep in PD patients does not modify the daytime sleepiness, thus suggesting that diurnal sleepiness may occur independently of nocturnal sleep disturbances in PD patients.