Objective: To investigate the impact of circadian rhythm (CR) and time of the day on the magnitude of motor impairments during gait initiation and continuation in people with Parkinson’s disease (PD).

Background: Based on increasing evidence that dopamine (DA) is involved in the regulation of CR and that decreased amplitude of CR after DA depletion may be linked to disruption of daily behavioral and physiological rhythms in PD, we hypothesized that disturbance of CR in PD patients would worsen their ability to appropriately initiate and maintain a functional gait pattern in the afternoon compared with the morning.

Methods: All participants were asked to wear an Acti-watch for seven consecutive 24-h periods. Wrist actigraphy was used as a measure of CR, and two main parameters (f-statistic and amplitude) were derived from an extended cosine model. For gait initiation study, an instructed-delay paradigm was used in which subjects were instructed to initiate walking as fast as possible, in response to a visual “go” cue. Ground reaction forces (GRFs) and center of pressure (CoP) excursions were recorded. Then, the same subjects were asked to walk on a split-belt treadmill at different belt-speed combinations, and stride length and stance time were measured. Both tasks were compared across two cohorts of subjects: PD patients (n=10), and control subjects (n=10), at two different times of day: 9am and 2pm (when CR generally peaks and dips in the day respectively). The time between dopaminergic medication intake and gait studies was precisely controlled in the PD group.

Results: Actigraphy results showed that the CR f-statistic and amplitude were significantly decreased in the PD group (p<0.05), which suggest that these patients suffered from CR dysfunction. In gait initiation study, CoP measures were significantly reduced and step onset was significantly delayed (p<0.05), in the afternoon session only in the PD group. PD patients also showed significantly more alterations and asymmetry in stride length, stance time and interlimb coordination (p<0.05) in the afternoon session, while the possible effects of medication fluctuation and fatigue were omitted by the study design.

Conclusions: The novel finding of our study was that PD patients’ impaired initiation and continuation of gait were more pronounced late in the day, and these changes were associated with their CR dysfunction.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/circadian-dysfunction-in-parkinsons-disease-effects-on-impaired-gait-initiation-and-locomotion/