title: The validity of the Gait Variability Index for individuals with mild to moderate Parkinson's disease.
abstract: Increased step-to-step variability is a feature of gait in individuals with Parkinson's disease (PD) and is associated with increased disease severity and reductions in balance and mobility. The Gait Variability Index (GVI) quantifies gait variability in spatiotemporal variables where a score ≥100 indicates a similar level of gait variability as the control group, and lower scores denote increased gait variability. The study aim was to explore mean GVI score and investigate construct validity of the index for individuals with mild to moderate PD. 100 (57 males) subjects with idiopathic PD, Hoehn & Yahr 2 (n=44) and 3, and ≥60 years were included. Data on disease severity, dynamic balance, mobility and spatiotemporal gait parameters at self-selected speed (GAITRite) was collected. The results showed a mean overall GVI: 97.5 (SD 11.7) and mean GVI for the most affected side: 94.5 (SD 10.6). The associations between the GVI and Mini- BESTest and TUG were low (r=0.33 and 0.42) and the GVI could not distinguish between Hoehn & Yahr 2 and 3 (AUC=0.529, SE=0.058, p=0.622). The mean GVI was similar to previously reported values for older adults, contrary to consistent reports of increased gait variability in PD compared to healthy peers. Therefore, the validity of the GVI could not be confirmed for individuals with mild to moderate PD in its current form due to low associations with validated tests for functional balance and mobility and poor discriminatory ability. Future work should aim to establish which spatiotemporal variables are most informative regarding gait variability in individuals with PD.
authors.affiliation: Research Department, Sunnaas Rehabilitation Hospital, Nesodden, Norway. Electronic address: linda.rennie@sunnaas.no.
authors.forename: Linda
authors.initials: L
authors.lastname: Rennie
authors.affiliation: Department of Neurology, Oslo University Hospital and Faculty of Medicine, University of Oslo, Norway. Electronic address: espen.dietrichs@medisin.uio.no.
authors.forename: Espen
authors.initials: E
authors.lastname: Dietrichs
authors.affiliation: Physiotherapy Research Group, Department of Global Public Health and Primary Health Care, University of Bergen, Norway. Electronic address: Rolf.Moe-Nilssen@uib.no.
authors.forename: Rolf
authors.initials: R
authors.lastname: Moe-Nilssen
authors.affiliation: Research Department, Sunnaas Rehabilitation Hospital, Nesodden, Norway; Institute of Neuroscience and Physiology, University of Gothenberg, Sweden; Habilitation & Health, Region Västra Götaland, Sweden. Electronic address: Arve.Opheim@vgregion.se.
authors.forename: Arve
authors.initials: A
authors.lastname: Opheim
authors.affiliation: Research Department, Sunnaas Rehabilitation Hospital, Nesodden, Norway; Karolinska Institutet, Department of Neurobiology, Care Sciences and Society, Division of Physiotherapy, Stockholm, Sweden; Functional Area Occupational Therapy & Physiotherapy, Allied Health Professionals Function, Karolinska University Hospital, Stockholm, Sweden. Electronic address: Erika.franzen@ki.se.
authors.forename: Erika
authors.initials: E
authors.lastname: Franzén
mesh_terms: D061725:Accelerometry; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D051346:Mobility Limitation; D010300:Parkinson Disease / Q000175:diagnosis / Q000503:physiopathology*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D016138:Walking / Q000502:physiology*
keywords: Balance; Construct validity; Gait Variability Index; Parkinson’s disease; Walking