Accelerated Progression of Gait Impairment in Parkinson's Disease and REM Sleep Without Atonia

Objective: People with Parkinson's disease (PD) and rapid eye movement (REM) sleep without atonia (RSWA) often have more severe gait disturbances compared to PD without RSWA. The association between the presence and expression of RSWA and the rate of progression of gait impairment in PD is unknown. This study examined the changes in spatiotemporal gait metrics over 3 years in people with mild-to-moderate PD (median 1.5 years since diagnosis at baseline) with (PD+RSWA, n = 16) and without RSWA (PD-RSWA, n = 14), and matched controls (n = 16). Methods: Steady-state gait metrics were obtained using a pressure-sensitive walkway at baseline and 3-year follow-up. RSWA scores were measured from electromyographic recordings during video-based polysomnography at baseline. Linear mixed models tested for the effects of visit, group, side (less vs. more affected), and their interactions. In people with PD, Spearman's correlations examined the relationship between baseline RSWA scores and the change in gait metrics. Results: Stride velocity variability was larger in PD+RSWA, compared to PD-RSWA and controls. Spatial and temporal measures of gait significantly worsened in both PD groups over 3 years. The PD+RSWA group showed a significantly larger decrement in step length (p < 0.05; mean = 7.9%) compared to PD-RSWA (2.6%) and controls (2.3%). Variability measures did not change significantly. In PD, the change in stride length correlated with chin RSWA scores at baseline. Interpretation: RWSA in early PD may be a harbinger of a more rapid progression in gait impairment, characterized primarily by a shortening of steps.