Abstract
Blood-based biomarkers of brain injury may be useful for monitoring brain health in athletes at risk for concussions. Two putative biomarkers of sport-related concussion, neurofilament light (NfL), an axonal structural protein, and S100 calcium-binding protein beta (S100B), an astrocyte-derived protein, were measured in saliva, a biofluid which can be sampled in an athletic setting without the risks and burdens associated with blood sampled by venipuncture. Samples were collected from men’s and women’s collegiate water polo players (n = 65) before and after a competitive tournament. Head impacts were measured using sensors previously evaluated for use in water polo, and video recordings were independently reviewed for the purpose of validating impacts recorded by the sensors. Athletes sustained a total of 107 head impacts, all of which were asymptomatic (i.e., no athlete was diagnosed with a concussion or more serious). Post-tournament salivary NfL was directly associated with head impact frequency (RR = 1.151, p = 0.025) and cumulative head impact magnitude (RR = 1.008, p = 0.014), while controlling for baseline salivary NfL. Change in S100B was not associated with head impact exposure (RR < 1.001, p > 0.483). These patterns suggest that repeated head impacts may cause axonal injury, even in asymptomatic athletes.
Highlights
Blood-based biomarkers of brain injury may be useful for monitoring brain health in athletes at risk for concussions
We examined associations between exposure to repetitive head impacts during a water polo tournament and changes in salivary expression of S100 calcium-binding protein beta (S100B) and neurofilament light (NfL), candidate protein biomarkers of astrogliosis and axonal damage in mild traumatic brain injury (mTBI)
Our primary novel finding is a dose–response relationship between the frequency and cumulative magnitude of head impacts sustained during a water polo tournament and changes in salivary NfL expression
Summary
Blood-based biomarkers of brain injury may be useful for monitoring brain health in athletes at risk for concussions. Change in S100B was not associated with head impact exposure (RR < 1.001, p > 0.483) These patterns suggest that repeated head impacts may cause axonal injury, even in asymptomatic athletes. Sport-related concussion is a specific form of mild traumatic brain injury (mTBI) caused by an impulsive force transmitted directly or indirectly to the head during athletic performance[1]. These insidious injuries are not reliably detected by common clinical imaging techniques or neuropsychological tests[2], leading to their classification as ‘mild’. Cumulative exposure to these impacts appears to contribute to the development of cognitive deficits many years later[5–7] To better understand these risks, it is first necessary to understand the acute physiological effects of exposure, over hours and days, even when an athlete appears to be asymptomatic. Several markers of central nervous system damage have been proposed as blood-based biomarkers for m TBI16–20
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