A Dose Relationship Between Brain Functional Connectivity and Cumulative Head Impact Exposure in Collegiate Water Polo Players

Abstract

A growing body of evidence suggests that chronic, sport-related head impact exposure can impair brain functional integration and brain structure and function. Evidence of a robust inverse relationship between the frequency and magnitude of repeated head impacts and disturbed brain network function is needed to strengthen an argument for causality. In pursuing such a relationship, we used cap-worn inertial sensors to measure the frequency and magnitude of head impacts sustained by eighteen intercollegiate water polo athletes monitored over a single season of play. Participants were evaluated before and after the season using computerized cognitive tests of inhibitory control and resting electroencephalography. Greater head impact exposure was associated with increased phase synchrony [r (16) > 0.626, p < 0.03 corrected], global efficiency [r (16) > 0.601, p < 0.04 corrected], and mean clustering coefficient [r (16) > 0.625, p < 0.03 corrected] in the functional networks formed by slow-wave (delta, theta) oscillations. Head impact exposure was not associated with changes in performance on the inhibitory control tasks. However, those with the greatest impact exposure showed an association between changes in resting-state connectivity and a dissociation between performance on the tasks after the season [r (16) = 0.481, p = 0.043] that could also be attributed to increased slow-wave synchrony [F (4, 135) = 113.546, p < 0.001]. Collectively, our results suggest that athletes sustaining the greatest head impact exposure exhibited changes in whole-brain functional connectivity that were associated with altered information processing and inhibitory control.

Salivary S100 calcium-binding protein beta (S100B) and neurofilament light (NfL) after acute exposure to repeated head impacts in collegiate water polo players

“…The present findings are also consistent with our previous report that changes in brain slow-wave synchrony over one season in water polo players is directly and linearly associated with the magnitude and frequency of head impacts (wCHI) and with frequency taken alone, i.e., without consideration of impact magnitude 47 . ‘Hyperconnectivity’ is theorized as a fundamental, compensatory response of brain functional networks in the face of microstructural perturbation 76 .…”

“…Our group has previously reported on the risks of head impact exposure in water polo, an intense, contact sport that carries a high risk of head, face, and neck injury, particularly at the elite level 43 , 44 . Specifically, we have observed that collegiate water polo players competing at the varsity and club levels sustain regular asymptomatic head impacts 45 , 46 , which may alter brain function in a dose-dependent manner over a competitive season 47 . However, the acute physiological effects of these impacts remain unknown.…”

One season of head-to-ball impact exposure alters functional connectivity in a central autonomic network

“…Thus, a strength of our study was the inclusion of control athletes that allowed for statistical correction of differences that might exist at baseline and also for natural changes that might occur over the course of a competitive season independent of head impact exposure. Our group recently reported a similar dose-response relationship between head impact exposure sustained by collegiate water polo players, increased coupling in whole-brain slow-rhythm oscillations, and a reduction in inhibitory control that was also suggestive of a shift away from proactive cognitive control strategies ( Monroe et al, 2020 ). Slow (delta rhythm) oscillations measured by electroencephalography are associated with basic homeostatic processes ( Knyazev, 2012 ), which means that the findings of the current study may corroborate those observations and support that repeated, sport-related head impact exposure is capable of disrupting the interface of central and autonomic nervous systems.…”

Incidence of Concussions in Elite Female Water Polo: A Retrospective Analysis

“…Conflicting evidence of the presence of concussion in collegiate players is emerging, 14 but there is a gap in studies on this topic at the international competitive level. 17,18 This discrepancy may be rooted in a lack of recognition of this pathology, because a recent study showed that knowledge on concussions can vary across countries and medical professionals. 19 Therefore, the primary goal of this study was to present the prevalence of concussions in a group of elite-level female water polo players over 10 years.…”