Scientists have long believed that a single traumatic brain injury (TBI) earlier in life could contribute to problems with depression, memory, and thinking ability later in life. This new study is the first to examine the role of repetitive head impacts, including those leading to “sub-concussive” injuries.
The study analyzed the records of 13,323 individuals age 40 and older who participated in the internet-based Brain Health Registry. Of the participants, 725 of the participants reported exposure to previous repetitive head impacts through contact sports, abuse, or military service. Researchers also examined the effects of having a TBI with and without loss of consciousness.
All participants were required to answer questionnaires regarding repetitive head impact, TBI history, and depressive symptoms. They were also given computerized cognitive tests.
The results, published in the journal Neurology, revealed that participants with a history of both repetitive head impacts and TBI reported greater depression symptoms than those who did not have such history. Repetitive head impacts and TBI were examined separately, and it was found that those with a history of repetitive head impacts had the strongest effect on later-life symptoms of depression.
“The findings underscore that repetitive hits to the head, such as those from contact sport participation or physical abuse, might be associated with later-life symptoms of depression. It should be made clear that this association is likely to be dependent on the dose or duration of repetitive head impacts and this information was not available for this study,” said Michael Alosco, Ph.D., associate professor of neurology at BU School of Medicine (BUSM) and co-director of the BU Alzheimer’s Disease Center Clinical Core.
A Cumulative Effect
Researchers found a dose-response-like pattern between head trauma and depression symptoms. A similar cumulative effect was also seen among those who had been exposed to repetitive head impacts and TBI on tests of cognitive function, including memory, learning, processing speed, and reaction time.
“These findings add to the growing knowledge about the long-term neurological consequences of brain trauma,” said Robert Stern, Ph.D., professor of neurology, neurosurgery and anatomy & neurobiology at BUSM and director of clinical research at the BU CTE Center. “It should be noted that not all people with a history of repetitive hits to the head will develop later-life problems with cognitive functioning and depression. However, results from this study provide further evidence that exposure to repetitive head impacts, such as through the routine play of tackle football, plays an important role in the development in these later-life cognitive and emotional problems,” added Stern, one of the senior authors of the study.
This study did have limitations, as the researchers did not have access to measurements or estimates of the degree of repetitive impact exposure or TBI frequency. The research team plans to extend their work through continued collaboration between BU and UCSF investigators utilizing data from the Brain Health Registry.