Impairment and disability: Their relation during stroke rehabilitation

Objectives: To describe the association between impairment and disability during stroke rehabilitation and to examine the effects of rehabilitation by studying the degree of disability reduction experienced by stroke patients who did not have significant reductions in impairment levels. Design: Statistical analysis of items from a database of prospectively collected information on stroke patients admitted for rehabilitation. Setting: Large urban academic freestanding rehabilitation facility. Participants: Four hundred two patients consecutively admitted for comprehensive acute stroke inpatient rehabilitation. Main Outcome Measures: The National Institutes of Health Stroke Scale (NIHSS) was used to measure impairment and the Functional Independence Measure (FIM(SM)) was used to measure disability. Motor and cognitive subscales of the FIM(SM) instrument were evaluated. Raw NIHSS and FIM(SM) scores were converted to linear measures using Rasch analysis. Methods: Relationships were studied between converted NIHSS and the two FIM(SM) subscales for admission, discharge, and change scores using linear regression analysis. In a second analysis, two groups of patients were identified; the 342 patients who experienced no substantial reduction of impairment comprised the 'no impairment reduction (NIR) group,' and the 60 patients who had a significant reduction of impairment level comprised the 'impairment reduction (IR) group.' Multivariate analysis of variance was used to determine and compare the amount of change in motor and cognitive FIM(SM) measures over time for each of the two groups. Results: NIHSS correlated significantly with motor and cognitive FIM(SM) subscores for admission, discharge, and change measures; R² values ranged between .02 and .36. Both the NIR group and the IR group experienced significant decreases in disability during rehabilitation. The differences in discharge FIM(SM) measures between the two groups were relatively small. Conclusions: Although stroke-related impairment and disability are significantly correlated with each other, reduced impairment level alone does not fully explain the reduced disability that occurs during rehabilitation. Even patients without substantial impairment reduction demonstrate disability reduction during rehabilitation, suggesting that rehabilitation has an independent role in improving function beyond that explained by neurologic recovery alone.