Researchers have been questioning and evaluating the long-term effects of concussion for several years. Early investigations typically implemented standard clinical assessments (eg, neurocognitive tests) in young adult athletes. In general, the findings from these studies indicated there were no significant differences between those with and without an injury. In one of these studies, the authors speculated that concussion did not have an effect on cognitive health beyond the acute stage of injury or the tools being used at the time were not sensitive to the subtle changes being brought about by injury.1 To date, the former is looking less and less likely and the latter more and more feasible.
The return to preinjury levels of functioning from concussion is thought to occur within 2 weeks in adults. This notion has been derived from the implementation of clinical tests in concussed athletes that evaluate concussion-related symptoms, postural control, and neurocognitive function. Although each of these tests is highly capable of evaluating gross declines following injury, they do not appear to be sensitive to subtle declines that persist for years after injury. For example, one investigation enrolled young adults with and without a concussion history. Those with a concussion history were, on average, 3.2 years postinjury. All participants completed a computer-based neurocognitive assessment that is commonly used for concussion management and the visual oddball task while event-related potentials (ERPs) (ie, cerebral activity) were being recorded. Similar to previous works, the results indicated no difference between the 2 groups on the neurocognitive evaluation. Surprisingly, the ERP evaluation indicated those with a concussion history showed lowered cerebral activation in relation to attentional resources and a decreased ability to suppress errant responses. Although these subtle changes were present in the concussion history group, they were not of the magnitude that changed the daily functioning of the participants.2
Second to this investigation was a study evaluating the effects of concussion on postural control. Athletes with a concussion history were, on average, 2.9 years postinjury, while a group of nonconcussed athletes served as controls. The preseason postural control evaluation yielded no differences in common balance measures, but subtle differences were noted between the 2 groups when their sway patterns were evaluated. That is, the concussed group showed a decline in the complexity of their mediolateral (ML) sway, suggesting that the nonconcussed group had more control of their ML movements.3 These changes parallel postural control declines reported in healthy older adults but also suggest that without intervention, those with a concussion history may be more susceptible to falls and further injury later in life.
A follow-up to the postural control investigation evaluated for changes in gait in young adults with and without a concussion history. In this study, the concussed group was 6 years postinjury. Each participant was evaluated on 4 gait conditions: with and without a brief cognitive task and/or stepping over an obstacle. The cognitive task was also completed while seated, but similar to other studies implementing cognitive tests, there were no differences between the 2 groups under any conditions. Gait variables that are typically evaluated (eg, speed, stance length, and width) did not differ between groups either. What did differ was the time spent in single-leg stance (ie, swing phase) and the time in double-leg stance. For these measures, the previously concussed group showed greater time in double-leg stance and less time in single-leg stance than the healthy participants. When viewed in conjunction with the balance findings above, the authors felt the previously concussed participants had adopted a more conservative and safer gait pattern to protect themselves from falls.4 Similar to the study on balance, this gait pattern is common among older adults who are otherwise injury free.
These study findings do not directly indicate that sustaining one or more concussions will result in cognitive function or motor control (ie, gait and balance) declines to a degree that will have a meaningful influence later in life. But if they do, the literature cited here suggests that concussion can no longer be thought of as a transient injury void of long-term consequences. However, caution is warranted. One cannot assume that just because an athlete sustains a concussion during high school, he or she is now predisposed to significant late-life cognitive decline. Indeed, research indicating that multiple concussions may result in higher rates of depression and mild cognitive impairment5,6 was conducted on professional athletes with years of exposure to subconcussive impacts and numerous unreported concussions. This is not the same level of exposure for the average individual.
However, even if the concussion sets the wheels in motion for decline, numerous factors will play a role. For example, the individual's genetic profile, family history of cognitive issues, exercise, and alcohol consumption, along with other factors, may influence cognitive change in a positive or negative manner over time.7 Importantly, the majority of individuals who sustain concussions during athletic events end their careers with high school, which appears to have no relation to later life changes.8 This is in contrast to highly publicized reports of professional athletes with decades of exposure to head impacts and concussions.
- Broglio SP, Ferrara MS, Piland SG, Anderson RB. Concussion history is not a predictor of computerized neurocognitive performance. Br J Sports Med. 2006;40(9):802–805. doi:10.1136/bjsm.2006.028019 [CrossRef]
- Broglio SP, Pontifex MB, O'Connor P, Hillman CH. The persistent effects of concussion on neuroelectric indices of attention. J Neurotrauma. 2009;26(9):1463–1470. doi:10.1089/neu.2008.0766 [CrossRef]
- Sosnoff JJ, Broglio SP, Shin S, Ferrara MS. Previous mild traumatic brain injury and postural control dynamics. J Athl Train. 2011;46(1):85–91. doi:10.4085/1062-6050-46.1.85 [CrossRef]
- Martini DN, Sabin MJ, DePesa SA, et al. The chronic effects of concussion on gait. Arch Phys Med Rehabil. 2011;92(4):585–589. doi:10.1016/j.apmr.2010.11.029 [CrossRef]
- Guskiewicz KM, Marshall SW, Bailes J, et al. Recurrent concussion and risk of depression in retired professional football players. Med Sci Sports Exerc. 2007;39(6):903–909. doi:10.1249/mss.0b013e3180383da5 [CrossRef]
- Guskiewicz KM, Marshall SW, Bailes J, et al. Association between recurrent concussion and late-life cognitive impairment in retired professional football players. Neurosurgery. 2005;57(4):719–726. doi:10.1227/01.NEU.0000175725.75780.DD [CrossRef]
- Broglio SP, Eckner JT, Paulson H, Kutcher JS. Cognitive decline and aging: the role of concussive and sub-concussive impacts. Exerc Sport Sci Rev. 2012;40(3):138–144.
- Savica R, Parisi JE, Wold LE, Josephs KA, Ahlskog JE. High school football and risk of neurodegeneration: a community-based study. Mayo Clin Proc. 2012;87(4):335–340. doi:10.1016/j.mayocp.2011.12.016 [CrossRef]