The effect of age on rehabilitation outcome after traumatic brain injury assessed by the Functional Independence Measure (FIM)

Background: The impact of age on rehabilitation outcome after traumatic brain injury (TBI) as measured by changes in the Functional Independence Measure (FIM) has been addressed in several seemingly conflicting reports. Differences may be explained by different study populations and different ways of analyzing data.

Objective: To investigate the role of data analysis in the interpretation of the age effect on rehabilitation outcome after TBI by comparing classical analyses of the total FIM score with a new item-wise analysis that unfolds the comprehensive amount of information contained in the FIM measurement otherwise concealed by the total score.

Methods: We analyzed admission and discharge FIM data from 411 consecutive TBI patients admitted to inpatient rehabilitation during 1998-2011 by both methods.

Results: The classical analysis indicated similar rehabilitation outcome in the 18 to 39, 40 to 64, and 65+ years age groups, which could be explained by selection of strong elderly patients and/or methodological problems with classical data analyses, whereas the item-wise analysis demonstrated profound age effect on most FIM items throughout the age interval covered.

Conclusions: The item-wise analysis meets requirements of proper data analysis, avoids concealing diversity in rehabilitation outcome behind the total FIM score, and provides a flexible, informative, and clinically relevant data analysis.