Meaningful change in measures of gait variability in older adults☆
Received 2 February 2009; received in revised form 29 September 2009; accepted 3 October 2009. published online 04 November 2009.
Abstract
Objectives
Gait variability is an important indicator of impaired mobility in older adults; however, little is known about the meaning of change in gait variability over time. This study estimated clinically meaningful change in measures of gait variability using both distribution- and anchor-based approaches.
Design
Community-based observational cohort study.
Setting
Bronx County and the research center at Albert Einstein College of Medicine.
Participants
Of 1148 participants in the Einstein Aging Study, 241 had quantitative gait assessments in two consecutive years between 2001 and 2005.
Measurements
Gait variables were collected using a 12-foot instrumented walkway as participants walked at their normal walking speed. Gait variability was defined as the within-person standard deviation (SD) across steps in two 12-foot walks. Distribution-based meaningful change estimates used Cohen's effect size (0.2 for small and 0.5 for moderate effects). Anchor-based estimates were obtained using dichotomous and ordinal self-reported walking ability ratings as anchors.
Results
Distribution-based estimates for small and substantial changes of variability measures were: stance time 0.005 and 0.014s; swing time 0.003 and 0.009s; step length 0.24 and 0.61cm; and step width 0.03 and 0.08cm. Among those reporting no change in walking ability, measures of gait variability were stable over 1 year. Among those reporting a decline in walking, stance time and swing time variability increased. Among those reporting an improvement in walking, only step length variability improved.
Conclusion
Preliminary criteria for meaningful change are 0.01s for stance time and swing time variability and 0.25cm for step length variability. These estimates may identify important changes over time in both clinical settings and research studies.
aDepartment of Physical Therapy, University of Pittsburgh, Pittsburgh, PA, United States
bDepartment of Medicine, Division of Geriatric Medicine, University of Pittsburgh, Pittsburgh, PA, United States
cDepartment of Neurology, Albert Einstein College of Medicine, Bronx, NY, United States
dDepartment of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY, United States
Corresponding author at: 6035 Forbes Tower, Pittsburgh, PA 15260, United States. Tel.: +1 412 383 6533; fax: +1 412 648 5970.
☆ Funding sources and related paper presentations: The Einstein Aging Study is supported by National Institutes on Aging program project grant (AG03949). J. Verghese is supported by a National Institutes on Aging grant (R01 AG025119). University of Pittsburgh Older American's Independence Center grant P30 AG024827-01. J.S. Brach is supported by a National Institutes on Aging and American Federation of Aging Research Paul Beeson Career Development Award (K23 AG026766).
ABSTRACT