Elsevier

Gait & Posture

Volume 41, Issue 4, May 2015, Pages 941-946
Gait & Posture

Validity of the Gait Variability Index in older adults: Effect of aging and mobility impairments

https://doi.org/10.1016/j.gaitpost.2015.03.349Get rights and content

Highlights

  • The Gait Variability Index is lower in older adults relative to younger adults.

  • The Gait Variability Index is lower in older adults with mobility deficits relative to high functioning older adults.

  • The Gait Variability Index is valid for assessing age-related decline of mobility function.

Abstract

Gait variability, defined as the fluctuation in spatiotemporal characteristics between steps, is suggested to be a sensitive indicator of mobility deficits with aging and pathological processes. A challenge in quantifying gait variability is the decision of which spatiotemporal parameters to assess because gait parameters may exhibit different amounts of variability and may differentially relate to mobility performance. The Gait Variability Index (GVI), a composite measure of variability across several gait parameters, was previously developed to overcome this challenge. The present study seeks to validate the use of GVI in the older adult population. A retrospective analysis of gait and clinical data was conducted using data pooled from five prior studies. The final data set included 105 younger adults (YA, age < 65) and 81 older adults (OA, age  65). The GVI of OA (91.92 ± 8.75) was significantly lower compared to the GVI of YA (100.79 ± 7.99). Within OA, the GVI was significantly lower (p < 0.0001) in individuals with mobility deficits (84.35 ± 9.03) compared to those with high mobility function (96.35 ± 8.86). Furthermore, GVI was associated with mobility function, including walking speed and performance on the Berg Balance Scale. Our findings imply that the GVI is a valid assessment for gauging spatiotemporal gait variability in older adults, is sensitive to differentiate between high-functioning older adults and those with mild to moderate mobility deficits and is associated with some clinical measures of functional mobility and balance.

Introduction

Gait variability, defined as the fluctuation in spatiotemporal characteristics between steps, is a sensitive indicator of mobility deficits [1]. For example, variability in spatiotemporal parameters is reported to predict mobility deficits and future falls better than the mean of spatiotemporal parameters in older adults [2]. Gait variability is altered by pathological conditions of disease and injury [3]. An investigation of the magnitude of these fluctuations has received considerable attention and is the focus of the current study. Particularly, the magnitude in gait variability is an important outcome measure in older adults since altered gait variability has shown to be associated with advancing age, mobility deficits, cognitive impairments and fall risk [4], [5], [6], [7]. A majority of the literature in older adults report that gait variability is increased in older adults [1]. However, decreased gait variability has also been reported in some spatiotemporal parameters (such as step width) and related to mobility deficits [8]. Despite the mounting evidence supporting use of gait variability as an outcome measure in the older adult population, there has been limited use of gait variability measures in clinical settings or in randomized controlled trials.

The lack of widespread use of gait variability as an outcome measure may, in part, be due to methodological challenges [9]. First, it is unclear which spatiotemporal measures are of greatest importance when assessing gait variability. Variability has been reported for at least 11 spatiotemporal parameters, but it is unclear which are most relevant to mobility function and the deficits that they reflect. For instance, step width variability was associated with age-related sensory impairments in a study by Brach et al. [10], whereas Richardson et al. reported that step time and not step width variability was associated with sensory impairments [11]. Second, there is a lack of consensus regarding how best to quantify gait variability [e.g., standard deviation (SD), coefficient of variation (CV)]. Some researchers have proposed that until a consensus can be reached, gait variability should be analyzed multiple ways [9]. Third, for individuals with impaired mobility the increase in gait variability can be observed across many different spatiotemporal parameters. This inter-dependence confounds statistical analysis because it is not clear which parameters are the best indicators of mobility deficits.

These methodological issues motivated the development of the Gait Variability Index (GVI). The GVI is a conglomerate measure of gait variability derived from nine spatiotemporal parameters and was developed to improve objective quantification of gait variability [12]. Preliminary validity was demonstrated by a decrease in GVI for individuals with Friedreich's Ataxia, suggesting that the GVI was linked to mobility function [12]. While the GVI seems to be a promising outcome measure because it avoids some of the methodological problems surrounding variability measures, it is not yet validated as an outcome measure in older adults. Therefore, the purpose of this study was to investigate the validity of the GVI as an outcome measure of mobility deficits in older adults.

Section snippets

Participants

This study retrospectively analyzed data pooled from 5 studies (Table 1). Participants aged 18–90 years (n = 186) were included. Participant data was categorized into two broad categories: younger adults (YA) less than 65 years of age and older adults (OA) greater than or equal to 65 years of age. Study protocols were approved by the Institutional Review Boards at the respective institutions and all participants gave their informed consent before participation.

Procedures

Procedures of included studies have

Results

Data reduction steps (i.e., ensuring enough steps to compute variability through GVI) resulted in a reduced data pool of 105 individuals in the YA group and 81 individuals in the OA group. The characteristics of the study pool and relevant characteristics of sub-groups of participants from each study are presented in Table 2.

Discussion

The GVI was previously developed as a composite measure to quantify the magnitude of variability in spatiotemporal parameters and demonstrated preliminary validity as an indicator of mobility deficits [12]. In the present study, GVI was validated as an indicator of age-related deficits in mobility function. Our study had 4 important findings: (1) GVI was significantly lower in older adults (age  65 years) compared to younger adults (age < 65 years), (2) decrements in GVI appeared to become

Conclusions

The GVI is a valid assessment for gauging the magnitude of spatiotemporal gait variability in older adults because (1) it is lower in older adults compared to younger, (2) seems to reduce with advancing age during the critical years where mobility deficits begin to emerge, (3) is capable of differentiating older adults who are high-functioning from those with mild to moderate mobility deficits, and (4) associates with some clinical measures of functional mobility and balance performance. Future

Acknowledgements

This study was supported in part by the Brooks Dean's Professorship Award which provided financial assistance for data collection of one of the included studies. Partial support was also provided by the University of Florida Claude D. Pepper Older Americans Independence Center (P30AG028740-04 and 2P30AG028740-06) and by the U.S. Department of Veterans Affairs Rehabilitation Research and Development Service (B7176W and B6793C) for two of other included studies.

Conflict of interest statement:

References (30)

  • J.S. Brach et al.

    Gait variability and the risk of incident mobility disability in community-dwelling older adults

    J Gerontol A Biol Sci Med Sci

    (2007)
  • M.L. Callisaya et al.

    Ageing and gait variability – a population-based study of older people

    Age Ageing

    (2010)
  • J.M. Hausdorff et al.

    Gait variability and basal ganglia disorders: stride-to-stride variations of gait cycle timing in Parkinson's disease and Huntington's disease

    Mov Disord

    (1998)
  • K.L. Martin et al.

    Cognitive function, gait, and gait variability in older people: a population-based study

    J Gerontol A Biol Sci Med Sci

    (2013)
  • T. Herman et al.

    Executive control deficits as a prodrome to falls in healthy older adults: a prospective study linking thinking, walking, and falling

    J Gerontol A Biol Sci Med Sci

    (2010)
  • Cited by (0)

    View full text