Functional recovery after severe traumatic brain injury: an individual growth curve approach

Objective: To examine person, injury, and treatment characteristics associated with recovery trajectories of people with severe traumatic brain injury (TBI) during inpatient rehabilitation.

Design: Observational prospective longitudinal study.

Setting: TBI rehabilitation units.

Participants: Adults (N=206) with severe nonpenetrating TBI admitted directly to inpatient rehabilitation from acute care. Participants were excluded for prior disability and intentional etiology of injury.

Interventions: Naturally occurring treatments delivered within comprehensive multidisciplinary teams were recorded daily in 15-minute units provided to patients and family members, separately.

Main outcome measures: Motor and cognitive FIM were measured on admission, discharge, and every 2 weeks in between and were analyzed with individual growth curve methodology.

Results: Inpatient recovery was best modeled with linear, cubic, and quadratic components: relatively steep recovery was followed by deceleration of improvement, which attenuated prior to discharge. Slower recovery was associated with older age, longer coma, and interruptions to rehabilitation. Patients admitted at lower functional levels received more treatment, and more treatment was associated with slower recovery, presumably because treatment was allocated according to need. Therefore, effects of treatment on outcome could not be disentangled from effects of case mix factors.

Conclusions: FIM gain during inpatient recovery from severe TBI is not a linear process. In observational studies, the specific effects of treatment on rehabilitation outcomes are difficult to separate from case mix factors that are associated with both outcome and allocation of treatment.