Abstract
BACKGROUND: Overall functional ability declines over time in people with Parkinson disease (PD). Established benchmarks are needed to allow clinicians and researchers to facilitate meaningful interpretation of data. OBJECTIVE: The purposes of this study were: (1) to report typical values for standard measures of functional ability commonly used in intervention studies and clinical practice with individuals in the early and middle stages of PD and (2) to describe the profile of functional limitations using the Hoehn and Yahr (H&Y) stages of disease and Unified Parkinson's Disease Rating Scale (UPDRS) motor scores. DESIGN: Cross-sectional data were obtained from 5 different studies. METHODS: Three hundred thirty-nine patients were evaluated for disease severity (UPDRS motor score); functional capacity (Continuous Scale Physical Functional Performance Test [CS-PFP]); balance and gait (Functional Reach Test [FRT], Timed "Up & Go" Test [TUG], 360-degree turn, Six-Minute Walk Test [6MWT], and Two-Minute Walk Test); and basic functional activities (supine-to-stand task, stand-to-supine task, and functional axial rotation [FAR]). RESULTS: The mean UPDRS motor score for the sample was 39.2 (SD=12.93). At each stage of PD (from least to most involved), scores on functional measures indicated a significant and progressively reduced functional status. Limitations began early in the disease for the CS-PFP and FAR. Losses in performance were consistent across all stages of disease for the CS-PFP, FRT, 6MWT, and FAR. Several measures demonstrated meaningful losses of function only in later stages of disease. Findings extend current appreciation of functional limitations that begin early in PD and can guide the choice of functional outcome measures at different stages of disease severity. LIMITATIONS: Data were obtained only from participants in H&Y stages 1 through 3 and only for some of the performance measures typically used. CONCLUSIONS: The findings demonstrate that functional loss occurs at different points in the disease process, depending on the task under consideration. The resulting profile of functional limitations provides benchmarks that clinicians and researchers can use to interpret and monitor status of patients.