A history of repetitive hits to the head (RHI), even without noticeable symptoms, is linked to a significantly increased risk of depression and poorer cognition later in life, new research shows.
“We found that a history of exposure to [repetitive hits to the head] from contact sports, military service, or physical abuse, as well as a history of TBI (traumatic brain injury), corresponded to more symptoms of later life depression and worse cognitive function,” lead author Michael Alosco, PhD, associate professor of neurology and codirector of the Boston University Alzheimer’s Disease Center Clinical Core, told Medscape Medical News.
He added that the findings underscore the importance of assessing repetitive head impacts (RHI).
The study was published online June 26 in Neurology.
Largest study to date
It is well known that sustaining a TBI is associated with worse later life cognition or mood problems, said Alosco. However, in the current research the investigators hypothesized that RHI may be a key driver of some of these outcomes, Alosco said.
Previous studies have been small or have only examined male former football players.
“What’s unique about our study is that we focused on a history of RHIs, and it is the largest study of its kind, incorporating over 30,000 males and females with different types of exposure to these RHIs.”
The researchers used data from the Brain Health Registry, an internet-based registry that longitudinally monitors cognition and functioning of participants (age 40 years and older).
Participants completed the Ohio State University TBI Identification Method (OSU TBI-ID) and answered a yes/no question: “Have you ever had a period of time in which you experienced multiple, repeated impacts to your head (eg, history of abuse, contact sports, military duty)?”
Participants also completed the Geriatric Depression Scale (GDS-15), the CogState Battery (CBB), and the Lumos Labs NeuroCognitive Performance Tests (NCPT). Demographic information included age, sex, race/ethnicity, and level of education.
Negative synergistic effect
Of the total sample (N = 13,323, mean age 62 years, 72.5% female, 88.6% White) 725 participants (5%) reported exposure to RHI, with contact sports as the most common cause, followed by physical abuse and then military duty; about 55% (7277 participants) reported TBI.
The researchers noted that 44.4% of those exposed to RHI and 70.3% of those who reported TBI were female. However, those with a history of contact sports were predominantly male and those reporting a history of abuse were predominantly women.
Among study participants who completed the GDS-15, 16.4% reported symptoms of depression, similar to rates reported among community-dwelling older adults.
Compared to the unexposed group, participants who reported TBI with loss of consciousness (LOC) and participants who reported TBI without LOC both had higher scores on the GDS-15 (beta = 0.75 [95% CI, 0.59-0.91] and beta = 0.43 [95% CI, 0.31-0.54], respectively).
A history of RHI was associated with an even higher depression score (beta = 1.24 [95% CI, 0.36-2.12).
Depression increased in tandem with increased exposure, with the lowest GDS-15 scores found in the unexposed group and subsequent increases in scores as exposure to RHI was introduced and TBI severity increased. The GDS scores were highest in those who had RHI plus TBI with LOC.
Participants with a history of RHI and/or TBI also had worse scores on tests of memory, learning, processing speed, and reaction time, compared with unexposed participants.
In particular, TBI with LOC had the most neuropsychological associations.
TBI without LOC had a negative effect on CogState tests measuring Identification and processing speed (beta = 0.004 [95% CI, 0-0.01] and beta = 0.004 [95% CI, 0.0002-0.01], respectively), whereas RHI predicted a worse processing speed score (beta = .02 [95% CI, 0.01-0.05]).
The presence of both RHI and TBI (with or without LOC) had a “synergistic negative effect” on neuropsychological performance, with a “consistent statistically significant finding” for worse neuropsychological test performance for those who had RHI and TBI with LOC, compared with those who had not sustained RHI.
Alosco said the findings highlight the need for clinicians to educate and inform parents/guardians of kids playing (or considering playing) contact sports about the research and potential risks associated with these activities.
If we want to prevent long-term problems, one way is not to expose [people] to these hits. Everyone takes risks in life with everything, but the more we can understand and mitigate the risks, the better,” Alosco said.