This articles covers research from the Transforming Research and Clinical Knowledge on Traumatic Brain Injury (TRACK-TBI) research initiative, whose mission is to better understand the mechanisms that underlie TBI disease progression, the clinical manifestations, and the short- and long-term outcomes of TBIs of all severities.
Recovery after traumatic brain injury (TBI) is not a one-size-fits-all process. While some individuals find that their symptoms resolve within days or weeks following injury, others find that their symptoms persist for months or even years. Although chronic TBI symptoms can be debilitating, researchers have very little knowledge about the factors that influence their duration of symptoms and eventual long-term outcomes.
A study from the Transforming Research and Clinical Knowledge on Traumatic Brain Injury (TRACK-TBI) research initiative explored the hypothesis that people who have sustained a TBI in the past are more likely to experience long-term symptoms after a recent TBI. A small study in 1975 found that people who had sustained two TBIs tended to experience cumulative effects; that is, the symptoms of the second TBI were made worse by the presence of the previous TBI, even when the initial injury had occurred in the distant past.
Since this 1975 study, most of the research on this topic has focused on populations that are vulnerable to sustaining multiple TBIs over short periods of time, such as athletes and combat service members. Data from both of these populations support the original 1975 finding: both groups seem to be at increased risk of long-term physical, cognitive, behavioral, and mood deficits. Furthermore, they are at higher risk of developing a neurodegenerative disease known as chronic traumatic encephalopathy (CTE), a common condition among professional football players.
The present study was unique because it examined non-athletes who had a previous history of TBI. This is an important distinction because non-athletes who have experienced TBI have a lower risk of exposure to multiple injuries in a short period of time, enabling researchers to determine if a single previous TBI can impact the outcomes of a second TBI.
Study participants provided information about their injury history, which researchers used to group them by whether or not they had previously experienced a TBI that was severe enough to cause loss of consciousness. The research team followed the subjects for six months after their current injury to determine their cognitive, psychological, and psychosocial outcomes, as well as their overall satisfaction with life.
The researchers found several differences between people who had previously experienced TBI and those who had not. Individuals with a history of TBI were more likely to admit to other health complaints such as musculoskeletal pain, neurological issues, developmental disabilities, and gastrointestinal problems. They were also more likely to have been treated for psychological conditions such as anxiety and depression, and were more likely to have been unemployed at the time of their current injury. According to the results of their six-month follow up, individuals with a previous TBI were more likely to experience more severe emotional distress, post-traumatic stress, and cognitive deficits. In general, they also were more likely to report poor satisfaction with life.
The results of this study provide important information about TBI patients who have a prior head injury. First, they indicate that even a TBI that occurred years prior to a current injury can affect outcomes related to the current injury. Second, the fact that the participants who reported a previous TBI also reported a greater degree of developmental disabilities suggests that the symptoms from their original injury did not fully resolve. Notably, the subjects who reported a previous TBI had lower injury severities than those patients without a prior history. This implies that their first injury could have caused long-term neurological and physiological deficits and suggests that, for patients with a history of TBI, even a minor head injury can have severe consequences.
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