Free-living gait characteristics in ageing and Parkinson's disease: impact of environment and ambulatory bout length

Abstract

Background: Gait is emerging as a powerful diagnostic and prognostic tool, and as a surrogate marker of disease progression for Parkinson's disease (PD). Accelerometer-based body worn monitors (BWMs) facilitate the measurement of gait in clinical environments. Moreover they have the potential to provide a more accurate reflection of gait in the home during habitual behaviours. Emerging research suggests that measurement of gait using BWMs is feasible but this has not been investigated in depth. The aims of this study were to explore (i) the impact of environment and (ii) ambulatory bout (AB) length on gait characteristics for discriminating between people with PD and age-matched controls.

Methods: Fourteen clinically relevant gait characteristics organised in five domains (pace, variability, rhythm, asymmetry, postural control) were quantified using laboratory based and free-living data collected over 7 days using a BWM placed on the lower back in 47 PD participants and 50 controls.

Results: Free-living data showed that both groups walked with decreased pace and increased variability, rhythm and asymmetry compared to walking in the laboratory setting. Four of the 14 gait characteristics measured in free-living conditions were significantly different between controls and people with PD compared to two measured in the laboratory. Between group differences depended on bout length and were more apparent during longer ABs. ABs ≤ 10s did not discriminate between groups. Medium to long ABs highlighted between-group significant differences for pace, rhythm and asymmetry. Longer ABs should therefore be taken into account when evaluating gait characteristics in free-living conditions.

Conclusion: This study provides encouraging results to support the use of a single BWM for free-living gait evaluation in people with PD with potential for research and clinical application.

Keywords: Accelerometer; Ambulatory activity; Body worn monitor; Free-living data; Gait; Parkinson’s disease.

Fig. 1

a Example of body worn monitor placement for both the laboratory based and free-living data collection. b Vertical acceleration and walking bout extraction (signal segments in black) from free-living data. c Example of gait characteristic extraction from walking bouts: detecting initial contacts (black stars) and final contacts (white circles). The black solid line represents vertical acceleration (a_v), the dashed line represents the differentiated with Gaussian CWT of a_v (a_vd), and the dotted line represents the differentiated with Gaussian CWT of a_vd (a_vdd). d Conceptual model of gait representing domains and 14 gait characteristics

Fig. 2

Summary flowchart of outcomes and methodology used for evaluation of the 14 gait characteristics of the gait model

Fig. 3

Radar plot illustrating the 14 gait characteristics organised by domain for people with Parkinson’s disease (PD) and controls (CL) evaluated in the laboratory (Lab). The central dotted line represents CL data, deviation from zero along the axis radiating from the centre of the plot represents how many standard deviations (range: ±2 SD, z score based on control means and standard deviations) the PD differ from CL. Asterisks represent significant differences between PD and CL (p values < 0.01)

Fig. 4

Radar plot illustrating the 14 gait characteristics organised by domain for people with Parkinson’s disease (PD) and controls (CL) evaluated in free-living conditions. The central dotted line represents CL data, deviation from zero along the axis radiating from the centre of the plot represents how many standard deviations (range: ± 2 SD, z score based on control means and standard deviations) the PD differ from CL. Asterisks represent significant differences between PD and CL (p values < 0.01)

Fig. 5

Mean number of walking bouts over seven days of recording for different ambulatory bout (AB) lengths (ABs ≤ 10s, 10s < ABs ≤ 20s, 20s < ABs ≤ 30s, 30s < ABs ≤ 60s, 60s < ABs ≤ 120 s, ABs > 120 s) for both people with Parkinson’s disease (PD, black) and controls (CL, white)

Fig. 6

Radar plot illustrating the 14 gait characteristics organised by domain for people with Parkinson’s disease (PD) and controls (CL) evaluated in free-living conditions for ambulatory bouts (ABs) ≤ 10s (panel (a)), 30s < ABs ≤ 60s (panel (b)), and ABs > 120 s (panel (c)). The central dotted line represents CL data, deviation from zero along the axis radiating from the centre of the plot represent how many standard deviations (range: ± 2 SD, z score based for each bout length on control means and standard deviations) the PD differ from CL. Asterisks represent significant differences between PD and CL (p values < 0.01)