This study examined the notion that mild to moderate traumatic brain injury (TBI) may have persistent effects that become evident upon neurocognitive testing in a phase in which the effects of physiological aging become manifest. Neurocognitive performance was tested in 25 middle-aged and 20 old subjects who had sustained mild to moderate TBI, on average, several decades earlier. The TBI subjects regarded them-selves as normal and healthy. The performance of the TBI subjects was inferior to that of matched healthy controls on all aspects of primary and secondary memory and on the majority of tests used to measure speed of performance. There was no interaction between the effects of TBI and those of age, and the performance of middle-aged TBI subjects was similar to that of old controls. The results are taken to indicate that TBI sustained earlier in life may cause permanent sequelae in specific domains of cognitive functioning and that it might attenuate the age-related decline in cognitive functioning. Most striking, however, was that these deficits were not perceived as a limiting factor in everyday life, which suggests that coping strategies may be important.
Klein, M., Houx, P. J., & Jolles, J. (1996). Long-term persisting cognitive sequelae of traumatic brain injury and the effect of age. The journal of nervous and mental disease, 184(8), 459-467. https://doi.org/10.1097/00005053-199608000-00002