|abstract ||Sleep disorders are highly prevalent among patients with Parkinson’s disease (PD). However, there are also reports of PD patients experiencing a beneficial effect of sleep. Upon awaking in the morning they experience an improved mobility as if they are in an “on” state due to medication, contrary to what would be expected after a night without medication. This intriguing phenomenon is known as sleep benefit (SB). Research on SB is limited and studies report divergent results. Variability in results can be mainly ascribed to differences in definitions and subjective measurements. SB has mostly been attributed to improved dopaminergic function as a result of increased storage of dopamine in nigral neuronal terminals during sleep. Contrarily, other authors claim that SB is probably unrelated to sleep, but associated with the time of awakening and pattern of motor fluctuations. In this thesis also a third hypothesis is introduced, that not sleep, but rather sleep deprivation facilitates SB. However, none of the current hypotheses can be sufficiently validated. Therefore, more research on the underlying mechanisms of SB is necessary.
In future research on SB the use of clear and standardized definitions is essential and an objective method should be used to measure SB. Furthermore, for a better understanding of SB it is important to explicitly study the underlying mechanisms of SB and determine which hypothesis is most feasible. The beneficial effects of SB might go beyond the improvement of motor symptoms. Therefore, it would be interesting to study the influence of SB on, for example, cognitive rigidity. Finally, more attention for the clinical implications and therapeutic applicability of SB might improve treatment of PD patients.|