For the past 16 years of living with Parkinson’s Disease (PD) I discovered that I frequently have great motor functioning upon awakening in the morning and that it often lasts about two hours.. Being without anti-PD meds all night, this is contrary to what I would expect. Although my hand tremor sometimes wakes me in the middle of the night, by the time I arise in the morning, my hand tremor has disappeared. Sometimes I don’t even feel like I have PD until a couple of hours later when I am rudely reminded that indeed I do have PD with my slow-moving, stiff body and shaky hands. But the brief respite from PD is heavenly.
Apparently, I am not alone. A new study has confirmed that in nearly half (46.9%) of people with PD, sleep improves their motor functioning, which seems to be better in the morning just after they have woken up. About a third (33.7%) of the study participants who regularly took naps, experienced a sleep benefit after taking a nap.
Some of the limitations of this and other studies are that they are based on subjective patient judgment in determining the presence of sleep benefit. In addition, sleep benefit may be confused with specific feelings of refreshment after sleep. Also, little is known about the how the subjective experience of improved motor functioning compares with objective testing, such as in the Unified Parkinson’s Disease Rating Scale (UPDRS).
Researchers came up with several possible reasons for the finding, though they noted that they do not know the exact underlying mechanisms. Several hypotheses have been proposed:
Sleep benefit has been attributed to improved dopamine functioning as a result of increased dopamine storage in neurons affected by PD during sleep (persons with Parkinson’s have low levels of dopamine).
Sleep benefit could be unrelated to sleep, but merely represents a morning benefit related to circadian rhythms.. However, the occurrence of sleep benefit after daytime naps suggests a specific role for sleep.
I think I’ll go and take a nap and get a little sleep benefit.
Source: Sleep Benefit in Parkinson’s Disease: Time to Revive an Enigma? in the Journal of Parkinson's Disease  1-4, DOI 10.3233/JPD-2012-12087 (Merrel van Gilst, Maartje Louter, Christian Baumann, Bastiaan Bloem, Sebastiaan Overeem).