rhi interval effects on brain health

Conditions: Repetitive Head Impacts

Summary: military service members frequently experience repetitive insults or impacts to the head (rhis). the purpose of the proposed randomized controlled trial is to understand how time intervals affect neurological responses to repetitive subconcussive head impacts.

this study will address whether, and to what extent, the interval of time between repetitive head impact (rhi) clusters (short, 24 hours; long, 72 hours) influences neuronal cellular, physiological, and functional integrity. we will leverage a human laboratory model of rhi to standardize and isolate the effects of rhi in the context of direction, magnitude, and frequency of head impact. there are three aims that navigate this study: aim 1: to determine the effect of the interval of time between rhi clusters on neural cellular and molecular integrities through expression profiles of biofluid proteomic and transcriptomic biomarkers. hypotheses: significant elevations in proteomic biomarkers will be observed acutely after experiencing rhi, and there will be cumulative increase in these biomarkers after 4 weeks of consistent exposure to rhi. the shorter interval of rhi clusters will yield greater degrees of biomarker changes as compared to the longer interval. aim 2: to examine the effect of the interval of time between rhi clusters on retinal and ocular-motor health, as assessed by retinal changes on optical coherence tomography (oct), convergence, and pupillometry. hypotheses: a shorter interval of rhi clusters will result in altered retinal coherence and declines in convergence and choice reaction time compared to a longer interval. after 4 weeks of recurring exposure to rhi, declines in retinal and ocular-motor health will persist for 2-week post rhi exposure in the shorter-interval group, but the longer-interval group will normalize by the 2-week post-rhi follow-up. aim 3: to determine the influence of the interval of time between rhi clusters in neuronal network as assessed by quantitative eeg and choice reaction time. hypotheses: a shorter interval of rhi clusters will induce greater changes in eeg output acutely and chronically after rhi exposure, compared to the longer interval. changes in eeg signals will persist for 2-week post rhi exposure in the shorter interval, but the changes will be normalized in the longer-interval group.

Eligibility criteria:
inclusion criteria: * current soccer player (intercollegiate, club, intramural, recreational). * at least 5 years of soccer heading experience (justification below). * ability to provide informed consent without a legally authorized representative (lar). exclusion criteria: * any head, neck, or face injury within the 6 months prior to enrollment, including concussions, that precludes participation in contact sports. * participants with eye conditions or diseases that could impact the blood vessels in the eye -such as but not limited to: glaucoma, macular degeneration, diabetic retinopathy. * determination that the participant is unsuitable for study entry or potentially unable to complete all aspects of the study based on the judgement of the investigator.

Keywords: subconcussive brain injury tbi soccer heading time interval