Levels of interleukin-6 (IL-6) and IL-1 receptor antagonist (IL-1RA) are significantly elevated 6 hours after concussion, and higher IL-6 levels are associated with slower recovery, according to a study of 41 high school and college football players with concussion. The findings were published online ahead of print July 3 in Neurology.
Dr. Timothy B. Meier
“With so many people sustaining concussions and a sizeable number of them having prolonged symptoms and recovery, any tools we can develop to help determine who would be at greater risk of problems would be very beneficial,” said study author Timothy B. Meier, PhD, assistant professor of neurosurgery at the Medical College of Wisconsin in Milwaukee, in a news release. “These results are a crucial first step.”
Symptoms of sport-related concussion typically resolve within 1-2 weeks but may last longer. Although prior studies have focused on biomarkers that are specific to brain injury, nonspecific inflammatory markers also may hold promise in predicting recovery after a mild traumatic brain injury, the authors said.
To examine whether acute elevations in serum inflammatory markers predict symptom recovery following sport-related concussion, Dr. Meier and his research colleagues enrolled 857 high school and college football players into a prospective cohort study. They included in their analyses 41 concussed athletes and 43 matched control athletes with an average age of 18 years. None of the concussed athletes lost consciousness, two had posttraumatic amnesia, and one had retrograde amnesia. The concussed athletes had a mean symptom duration of 8.86 days.
The researchers measured serum levels of IL-6, IL-1RA, IL-1 beta, IL-10, tumor necrosis factor, C-reactive protein, and interferon-gamma and recorded Sport Concussion Assessment Tool, 3rd edition, symptom severity scores.
Participants with concussion underwent testing at the start of the season, within 6 hours of injury, 24-48 hours after injury, and at 8, 15, and 45 days after injury. Control athletes underwent testing at similar times.
Among athletes with concussion, IL-1RA and IL-6 were elevated at 6 hours, compared with all other postinjury visits and with controls. IL-6 and IL-1RA significantly discriminated concussed from control athletes at 6 hours postconcussion with an area under the receiver operating characteristic curve of 0.79 for IL-6 and 0.79 for IL-1RA. Furthermore, IL-6 levels at 6 hours significantly correlated with symptom duration, “with a 1-unit increase in natural log-transformed IL-6 associated with 39% lower hazard of symptom recovery,” the researchers reported.
The extent to which these results generalize to females, youth athletes, or athletes who develop postconcussion syndrome is unclear, and larger studies may be needed to adequately assess inflammatory markers as clinical biomarkers of sport-related concussion, the authors noted.
“Eventually, these results may help us better understand the relationship between injury and inflammation and potentially lead to new treatments,” Dr. Meier said.
The research was supported by the U.S. Department of Defense, National Institute of Neurological Disorders and Stroke, National Institute of General Medical Sciences, National Institute of Mental Health, and the National Center for Advancing Translational Sciences. The authors had no relevant disclosures.
SOURCE: Nitta ME et al. Neurology. 2019 Jul 3. doi: 10.1212/WNL.0000000000007864.