New research has found that even a years-old mild concussions can have long-lasting effects on brain function and behavior in otherwise healthy people. The study adds to a growing understanding of traumatic brain injury and is relevant to the evolving legal landscape around brain injuries in sports.
A concussion is a mild form of traumatic brain injury (TBI) resulting from events like falls, car crashes, contact sports, or assaults. The resulting disruption to brain function is often thought to be temporary. However, evidence is mounting that TBI is a risk factor for dementia, prompting research led by the University of Cambridge in the UK to investigate how the brain fares in the long term following a TBI, even a mild one.
They recruited 617 healthy middle-aged UK adults aged 40 to 59 as part of the Prevent Dementia study. Participants underwent MRI scans and neuropsychological testing to assess brain structure and function and their TBI history was assessed using the Brain Injury Screening Questionnaire (BISQ). TBI was defined as having experienced at least one blow to the head resulting in a loss of consciousness. Mild TBI was defined as a loss of consciousness of less than 30 minutes. The risk of cardiovascular disease was also assessed.
Of the 617 participants, 36.1% reported at least one TBI with a loss of consciousness. Of those, 56.1% reported a single TBI event, 27.4% reported two TBI events, and 16.6% reported more than two. Of the 223 participants with a history of TBI, injury severity was determined for 76.2%, of which 94.1% reported a mild TBI and 5.9% reported moderate-severe incidents that included a loss of consciousness of 30 minutes or longer.
Cerebral microbleeds – small, chronic brain hemorrhages – were detected in about one in six participants (17.7%). Compared to those without a TBI, the number of microbleeds was greater in participants with prior TBI, including those with mild TBI. Greater numbers of TBI events were associated with poorer sleep, gait disturbances, greater depression symptoms, and memory deficits but not deficits in attention. The mild TBI group had poorer sleep, depression, and gait but no cognitive effects.
The researchers examined the relative contribution of TBI and cardiovascular risk factors (for example, high blood pressure, diabetes) to these clinical deficits and found that TBI was the most important factor contributing to depression and sleep (but not cognition or gait), outweighing the contribution of cardiovascular risk factors. While TBI dominated cardiovascular risk factors in contributing towards memory deficits, the main dominating factors were sex and age.
“These data demonstrate that in otherwise healthy middle-aged adults, remote TBI history was associated with detectable changes in vascular brain imaging and clinical features,” said the researchers. “Overall, our findings have important implications for future research directions, as well as informing clinical practices and policymaking at the community level.”
In terms of informing clinical practices, the researchers say that undertaking TBI assessments in circumstances where someone is known to have had a brain injury could help ascertain which patients are at higher risk and enable treatment of their symptoms earlier.
The issue of TBI in sports has become a major concern in recent years, as more and more evidence has emerged about the short-, medium-, and long-term consequences of damage caused by such injuries. Most examples come from contact sports like boxing and martial arts, soccer, hockey, and football and, as a result, the legal landscape around this issue has changed.
