Longitudinal changes of brain microstructure and function in nonconcussed female rugby players

Abstract

ObjectiveTo longitudinally assess brain microstructure and function in female varsity athletes participating in contact and noncontact sports.MethodsConcussion-free female rugby players (n = 73) were compared to age-matched (ages 18–23) female swimmers and rowers (n = 31) during the in- and off-season. Diffusion and resting-state fMRI (rs-fMRI) measures were the primary outcomes. The Sports Concussion Assessment Tool and head impact accelerometers were used to monitor symptoms and impacts, respectively.ResultsWe found cross-sectional (contact vs noncontact) and longitudinal (in- vs off-season) changes in white matter diffusion measures and rs-fMRI network connectivity in concussion-free contact athletes relative to noncontact athletes. In particular, mean, axial, and radial diffusivities were increased with decreased fractional anisotropy in multiple white matter tracts of contact athletes accompanied with default mode and visual network hyperconnectivity (p < 0.001). Longitudinal diffusion changes in the brainstem between the in- and off-season were observed for concussion-free contact athletes only, with progressive changes observed in a subset of athletes over multiple seasons. Axial diffusivity was significantly lower in the genu and splenium of the corpus callosum in those contact athletes with a history of concussion.ConclusionsTogether, these findings demonstrate longitudinal changes in the microstructure and function of the brain in otherwise healthy, asymptomatic athletes participating in contact sport. Further research to understand the long-term brain health and biological implications of these changes is required, in particular to what extent these changes reflect compensatory, reparative, or degenerative processes.

Brain Metabolite Levels in Sedentary Women and Non-contact Athletes Differ From Contact Athletes

“…This difference found only in the contact athletes suggests that the contact nature of the sport is having a cumulative effect on the brain, as described by others (Koerte et al, 2012;Mayer et al, 2015;Lefebvre et al, 2018). To confirm that the contact athletes were indeed receiving high impacts, a head impact sensor that measures linear acceleration and rotational velocity was worn by a subset of players during a preseason rugby game (Manning et al, 2020). During this single rugby game, a total of 151 impacts exceeding 15 g were recorded across 26 players.…”

“…Six months was chosen because concussion symptom resolution typically occurs within a month, ensuring no athletes with chronic postconcussion syndrome were included. Athletes were recruited from the women's varsity rugby team over the course of five seasons, and women's varsity rowing and swim teams over a single season as describe previously (Schranz et al, 2018;Manning et al, 2020). Other exclusion criteria included any preexisting systemic disease (e.g., diabetes, autoimmune diseases, immunosuppressed subjects), any history of head or eye injury involving metal fragments, and implanted electrical devices (e.g., cardiac pacemaker).…”

“…Briefly, of the 54 rugby athletes, 14 played two consecutive seasons, 9 played three consecutive seasons, and one played two seasons, interspersed with a season of non-play. Additionally, the results of the SCAT3 scores for the contact and non-contact teams are reported in Manning et al (2020) and Schranz et al (2018).…”

“…Therefore, on average, a single player received six impacts >15 g per practice, and two impacts >15 g per game. Detailed results on the impact data can be found in Manning et al (2020). It is important to recognize that previous studies reporting higher impact rates used a threshold of >10 g (King et al, 2015(King et al, , 2018, rather than the >15 g used in this cohort of athletes.…”

“…Much less is known about the effect of repeated sub-concussive head impacts from physical contact in sport, particularly in female athletes (McGroarty et al, 2020). Such impacts are generally thought to be inconsequential, but may lead to subtle changes in brain metabolism and function (Manning et al, 2020). Detecting such effects must account for potential beneficial changes induced by exercise.…”