Neurofilament Light Not Associated With Concussion History Or Recency In Special Operations Forces Combat Soldiers

Abstract

Special Operations Forces (SOF) combat soldiers sustain high rates of blast and blunt neurotrauma. Most are mild traumatic brain injuries (i.e., concussion). Repetitive concussions may develop long-term neurological sequelae. Detecting the effects of cumulative exposure to concussion may be helpful to recognize and intervene therapeutically before chronic symptoms begin emerging. Neurofilament light chain (NfL) is an abundantly expressed cytoskeletal component of large caliber myelinated subcortical axons. Peripheral increases may indicate ongoing axonal disruption or chronic repetitive white matter injury within the brain. PURPOSE: To determine the effects of concussion history, lifetime incidence, and recency on NfL concentrations in SOF combat soldiers. METHODS: 185 SOF combat soldiers (age=33.0±3.5 yrs) participated in our cross-sectional study and self-reported concussion history (90 no, 95 yes), lifetime incidence (0, 1, 2, 3+) and recency (<1 month, <1 year, >1 year). Fasted blood samples were obtained from an antecubital vein at a standardized time for all subjects. Serum was separated and stored until analysis. Serum NfL levels were quantified using sandwich enzyme immunoassay kits according to manufacturer instruction. Medians and interquartile ranges (IQRs) were reported because NfL concentrations were not normally distributed. A Wilcoxon rank-sum analysis compared NfL concentrations between those with and without concussion history. Kruskal-Wallis tests compared NfL concentrations across lifetime incidence and recency. RESULTS: We did not observe differences in NfL concentrations (z=1.80, p=0.07) between those with (median=449.7 pg/mL, IQR=192.1) and without (median=484.4 pg/mL, IQR=221.2) concussion history. There was no effect of concussion lifetime incidence (X2(3)=3.87, p=0.28) or recency (X2(2)=0.86, p=0.65) on serum NfL concentrations. CONCLUSION: We did not observe differences in serum NfL concentration in SOF combat soldiers based on concussion history, lifetime incidence, and recency. Our SOF combat soldiers were otherwise healthy and asymptomatic. Despite this, our findings suggest SOF combat soldiers demonstrated higher NfL concentrations than those reported for civilian severe brain injury and neurodegenerative disease patients. Funded by USASOC