In the largest study of its kind, a link has been found in living patients exposed to repetitive head impacts and difficulties with cognitive functioning and depression years or decades later.
Scientists have long believed that a single traumatic brain injury (TBI) earlier in life may contribute to problems with memory, thinking, and depression later in life. Most previous studies, however, failed to examine the role of repetitive head impacts, including those leading to “subconcussive” injuries, in these problems later in life, according to researchers.
That led scientists from the Boston University Alzheimer’s Disease and Chronic Traumatic Encephalopathy Centers, the University of California, San Francisco, and San Francisco VA Healthcare System to team up to analyze the records of 13,323 individuals age 40 and older who participate in the internet-based Brain Health Registry.
Of those, 725 or 5 percent reported exposure to previous repetitive head impacts through contact sports, abuse, or military service, according to the analysis.
In addition to repetitive head impact history, the scientists also examined the effects of having a TBI with and without loss of consciousness.
Along with self-reported questionnaires of repetitive head impact and TBI history, participants completed measures of depressive symptoms and computerized cognitive tests.
The findings, published in the journal Neurology, revealed that participants with a history of both repetitive head impacts and TBI reported greater depression symptoms.
In addition, when repetitive head impacts and TBI were examined separately, a history of repetitive head impacts had the strongest effect on later-life symptoms of depression, according to the study’s findings.
The findings were independent of age, sex, racial identity, and education level, the researchers added.
“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., an associate professor of neurology at Boston University School of Medicine and co-director of the BU Alzheimer’s Disease Center Clinical Core.
There was a dose-response-like pattern between head trauma and depression symptoms, the researchers discovered.
Participants without any history of either TBI or repetitive head impacts had the fewest symptoms. While depression symptoms increased when a history of TBI alone was present, depression symptoms were highest for the participants who had a history of both repetitive head impacts and TBI.
Additionally, the participants who had a history of repetitive head impacts and TBI with loss of consciousness reported the most depressive symptoms, the researchers reported.
A similar cumulative effect was seen among those exposed to repetitive head impacts and TBI on tests of memory, learning, processing speed, and reaction time. Participants with a history of repetitive head impacts or TBI had a worse performance on some of the tests compared to those without any head trauma history, and those with both a history of repetitive head impacts and TBI with loss of consciousness had worse performance on almost all of these computerized cognitive tests, the analysis discovered.
“These findings add to the growing knowledge about the long-term neurological consequences of brain trauma,” said Robert Stern, Ph.D., a professor at Boston University School of Medicine and director of clinical research at the university’s Chronic Traumatic Encephalopathy 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.”