Article

OBJECTIVES: To examine the influence of cognitive reserve-related moderator
variables on recovery trajectories during the first year after traumatic brain
injury (TBI). Using mixed effects models, we measured (1) the level of cognitive
function at 2 and 12 months postinjury and (2) the trajectories of cognitive
recovery during the first 12 months postinjury. DESIGN: Repeated-measures design
with neuropsychological testing at 2, 5, and 12 months postinjury. SETTING:
Large, urban inpatient neurorehabilitation program. PARTICIPANTS: Patients (N=75)
with moderate-to-severe TBI. INTERVENTIONS: Not applicable. MAIN OUTCOME
MEASURES: Primary outcomes: neuropsychological composite scores including simple
speed of processing, complex speed of processing, memory, untimed executive
functions, and attention span. Primary predictors: age, estimated premorbid
intelligence quotient (IQ), and years of education. RESULTS: Only age
significantly moderated trajectories. Decreasing age significantly enhanced
recovery of speed of processing, both simple (2-12mo postinjury, P<.001) and
complex (2-12mo postinjury, P<.05; 5-12mo postinjury, P<.005). Decreasing age and
increasing estimated premorbid IQ were associated with higher performance at 2
and 12mo postinjury for simple speed of processing (premorbid IQ, 2 and 12mo),
complex speed of processing (age, 2 and 12mo), untimed executive functions
(premorbid IQ, 2 and 12mo), and memory (premorbid IQ, 2 and 12mo). CONCLUSIONS:
Recovery of speed of processing (both simple and complex) was favorably moderated
by younger age. Older age is associated with more neuronal loss and less
integrity of white matter, and speed of processing is associated with white
matter networks. The recuperative effects of younger age may therefore be
attributable to greater reserve capacity (as indexed by white matter integrity).
Lower age and higher estimated premorbid IQ were associated with higher
functioning on a variety of cognitive outcomes. This may reflect the buffering
effects of reserve capacity or premorbid differences in age and IQ-related
cognitive functioning. Implications for rehabilitation and recovery mechanisms
are discussed.

Langue : ANGLAIS