Cognitive Reserve and Age Predict Cognitive Recovery after Mild to Severe Traumatic Brain Injury

The persistence of injury-related cognitive impairments can have devastating consequences for everyday function after traumatic brain injury (TBI). This longitudinal study examined the association of long-term cognitive recovery in 109 adults (71% male) experiencing complicated mild-to-severe TBI with age, pre-morbid intelligence (IQ), and injury severity measured by post-traumatic amnesia (PTA) duration. Participants' twice completed measures of pre-morbid IQ (National Adult Reading Test), attention (Digit Symbol Coding Test), memory (Rey Auditory Verbal Learning Test), and executive function (Trail Making Test Part-B) at a mean of 43.73 days post-TBI and again at a mean of 3.70 years (range 23-72 months) post-injury. A healthy control group comprising 63 adults (59% male) completed the measures once. At initial assessment, TBI participants performed significantly worse on all measures compared with the healthy control group. Within the TBI group, shorter PTA duration, younger age, and higher pre-morbid IQ were associated with better initial cognitive performance. Cognitive task performance improved significantly in the TBI group at follow-up between two to five years later but remained significantly below control group means. Notably, higher pre-morbid IQ and younger age were associated with greater cognitive recovery at follow-up, whereas PTA duration was not. These findings support the role of cognitive reserve and age in cognitive recovery after TBI and may inform prognostication and rehabilitation. Additional research is needed to elucidate the biological mechanisms of cognitive reserve in cognitive recovery after TBI.