Predicting military readiness using objective and subjective indices of neuropsychological impairment in service members with mild traumatic brain injury

The military is interested in identifying factors to improve the readiness of service members with traumatic brain injury (TBI). TBI outcome studies have primarily used objective neuropsychological data interpreted using the absolute level of functioning (i.e., high average, average, low average), though research suggests it is also important to consider other objective indices of the relative degree of decline (e.g., mild, moderate, severe) and subjective complaints. The current study determined the predictive ability of objective indices of neuropsychological functioning (i.e., absolute level and the relative degree of decline) and subjective complaints (i.e., Neurobehavioral Symptom Inventory) in terms of military work status (i.e., return to duty, medically disabled, retired) for 113 service members with mild TBI. ANOVAs and post-hoc tests indicated individuals who were able to return to duty had higher absolute indices and lower relative decline scores in working memory and overall intelligence, as well as lower subjective neuropsychological complaints when compared to those who were disabled or retired. Multinomial logistic regression models generally supported these findings, except relative decline scores were not predictive of military work status likely due to issues of collinearity (i.e., relative decline scores are calculated using absolute scores). In conclusion, indices of absolute functioning and subjective neuropsychological impairments appear to be predictors of the ability to return to duty post-TBI in military populations, emphasizing the need to focus on cognitive reserve and emotional resilience as potential interventions.

Comparing indices of objective and subjective neuropsychological impairments in service members with mild traumatic brain injury

Neuropsychological impairments are evaluated using subjective measures and objective tests, although their relationship remains unclear. This is likely because objective data is interpreted in terms of absolute level of functioning (e.g., high average, average, low average) while subjective complaints are interpreted in terms of relative decline from premorbid levels (e.g., mild, moderate, severe). The current study calculated objective indices of estimated degree of relative decline (i.e., difference between current cognitive ability and estimated premorbid level) to compare objective and subjective indices of relative decline for military service members with mild traumatic brain injury (mTBI). Contrary to hypotheses, more indices of absolute level of functioning were significantly correlated with subjective neuropsychological (i.e., Neurobehavioral Symptom Inventory) and psychological complaints (e.g., Personality Assessment Inventory) than relative decline scores. The results suggest stronger cognitive abilities may be associated with greater cognitive reserve or emotional resilience and, thereby, less subjective complaints for individuals with TBI, regardless of the extent of neuropsychological decline experienced.