Six-Minute Walk Distance in Persons With Parkinson Disease: A Hierarchical Regression Model

Falvo MJ, Earhart GM. Six-minute walk distance in persons with Parkinson disease: a hierarchical regression model. Objectives: To determine the six-minute walk distance (6MWD) in subjects with Parkinson disease (PD) and to determine the impairments that contribute to walking capacity. Design: Descriptive cross-sectional study of subjects with PD. Setting: University laboratory. Participants: Subjects with PD (N=75; 65.0±9.5y) of mild to moderate severity, as defined by an average Hoehn and Yahr (HY) rating of 2.0±0.4 and Unified Parkinson Disease Rating Scale (UPDRS) motor score of 27±8.9, were tested on medication. Interventions: Not applicable. Main Outcome Measures: Subjects were administered the motor subsection of the UPDRS and completed the following tests: Berg Balance Scale (BBS), Timed Up & Go (TUG), and six-minute walk test. In addition, they also provided self-reports of freezing of gait and number of falls in the past 6 months. Results: The average 6MWD was 391.6±99.9m. All of the aforementioned tests, with the exception of fall number (P=.07), correlated significantly with 6MWD (r range, -.64 to .55). By using a hierarchical regression model, we entered age, HY, and UPDRS motor score into the first block (ie, set of independent variables) to represent parkinsonian characteristics, which explained a significant amount of variability in 6MWD (R²=.196, P<.001). The second block entered (eg, functional measures scores, self-reports) explained a significant amount of additional variability (R² change=.355, P<.001). The TUG, BBS, and number of falls contributed independently in the presence of all independent variables. Conclusions: The 6MWD in subjects with PD is explained in part by disease-specific characteristics and perhaps to a greater extent by impaired balance and predisposition to falling. Training targeted at improving balance and reducing falling risk factors may increase 6MWD (ie, walking capacity) in subjects with PD.