Investigating the Validity of the Environmental Framework Underlying the Original and Modified Dynamic Gait Index.

Background. The modified Dynamic Gait Index (mDGD, developed from a person-environment model of mobility disability, measures mobility function relative to specific environmental demands. The framework for interpreting mDGI scores relative to specific environmental dimensions has not been investigated. Objective. The aim of this study was to examine the person-environmental model underlying the development and interpretation of mDGI scores. Design. This was a cross-sectional, descriptive study. Methods. There were 794 participants in the study, Including 140 controls. Out of the total study population, 239 had sustained a stroke, 140 had vestibular dysfunction, 100 had sustained a traumatic brain injury, 91 had gait abnormality, and 84 had Parkinson disease. Exploratory factor analysis was used to investigate whether mDGI scores supported the 4 environmental dimensions. Results. Factor analysis showed that, with some exceptions, tasks loaded on 4 underlying factors, partially supporting the underlying environmental model. Limitations. Limitations of this study included the uneven sample sizes in the 6 groups. Conclusions. Support for the environmental framework underlying the mDGI extends its usefulness as a clinical measure of functional mobility by providing a rationale for interpretation of scores that can be used to direct treatment and infer change in mobility function.