Gait dynamics in Parkinson's disease: common and distinct behavior among stride length, gait variability, and fractal-like scaling

Abstract

Parkinson's disease (PD) is a common, debilitating neurodegenerative disease. Gait disturbances are a frequent cause of disability and impairment for patients with PD. This article provides a brief introduction to PD and describes the gait changes typically seen in patients with this disease. A major focus of this report is an update on the study of the fractal properties of gait in PD, the relationship between this feature of gait and stride length and gait variability, and the effects of different experimental conditions on these three gait properties. Implications of these findings are also briefly described. This update highlights the idea that while stride length, gait variability, and fractal scaling of gait are all impaired in PD, distinct mechanisms likely contribute to and are responsible for the regulation of these disparate gait properties.

Figure 1

Fall rates in PD, as observed in four prospective studies, compared to age-matched controls. Despite the differences in duration of follow-up (3–12 months), a fairly consistent pattern emerges. Falling incidence increases with longer follow-up and are much larger than those observed in controls [From B. R. Bloem, J. M. Hausdorff, J. E. Visser, and N. Giladi, “Falls and freezing of gait in Parkinson’s disease: A review of two interconnected, episodic phenomena,” Mov Disord. 19, 871 (2004). Copyright ©2004 by Movement Disorder Society. Reprinted by permission of John Wiley & Sons, Inc.].

Figure 2

Clinical impact of instability and falls in patients with PD. Note the vicious cycle that arises as a result of gait instability and impairment [From B. R. Bloem, J. M. Hausdorff, J. E. Visser, and N. Giladi, “Falls and freezing of gait in Parkinson’s disease: A review of two interconnected, episodic phenomena,” Mov Disord. 19, 871 (2004). Copyright ©2004 by Movement Disorder Society. Reprinted by permission of John Wiley & Sons, Inc.].

Figure 3

(a) Example of time series of stride time during 1 h of walking in a healthy young adult at slow, normal, and fast walking rates, and below, after the fast data set is randomly shuffled. (b) While there are subtle effects of gait speed, DFA shows that there is fractal scaling at all three gait speeds. When the data are randomly reordered (shuffled), the slope becomes 0.5, reflecting white noise and an absence of fractal scaling [From J. M. Hausdorff, P. L. Purdon, C. K. Peng, Z. Ladin, J. Y. Wei, and A. L. Goldberger, “Fractal dynamics of human gait: stability of long-range correlations in stride interval fluctuations,” J. Appl. Physiol. 80, 1448 (1996). Copyright ©1996 by American Physiological Society. Reprinted by permission of American Physiological Society]. Data can be downloaded from www.physionet.org. Strictly speaking, Figs. 345 should be plotted as discrete points rather than points joined with lines. The points are joined together as a continuous line, however, since this makes it somewhat easier to visualize the dynamics.

Figure 4

Gait rhythm dynamics in a patient with PD. On the left, time series are shown before (original) and after random reordering of the data. Note that the temporal structure of the time series looks similar before and after reordering. This impression is confirmed using DFA (right). The slopes for the original data and the reordered data set are both close to white noise (0.5).

Figure 5

Example of swing time series from a patient with PD and a control under usual walking conditions and when performing serial 7 subtractions. Under usual walking conditions, variability is larger in patient with PD (CV=2.7%) compared to the control (CV=1.3%). Variability increases during dual tasking in the subject with PD (CV=6.5%) but not in the control (CV=1.2%) [From G. Yogev, N. Giladi, C. Peretz, S. Springer, E. S. Simon, and J. M. Hausdorff, “Dual tasking, gait rhythmicity, and Parkinson’s disease: Which aspects of gait are attention demanding?,” Eur. J. Neurosci. 22, 1248 (2005). Copyright ©2005 Federation of European Neuroscience Societies. Reprinted by permission of Blackwell Publishing].