Dynamic cerebral autoregulation remains preserved in professional boxers

Background and hypothesis: Chronic traumatic encephalopathy (CTE) associated with boxing is characterised by progressive impairment in cognitive, behavioral and motor function as a consequence of repetitive impact to the brain. Given that symptoms typically present long after the cessation of a boxer's career, early diagnosis has the potential to reduce the risk of developing CTE. Traditionally, much emphasis has focused on neuro-anatomical correlates (McCrory et al., 2007) to the exclusion of potential abnormalities in cerebral haemodynamic function. In the current study, we tested the hypothesis that dynamic cerebral autoregulation (dCA) would be impaired in boxers and thus provide a more sensitive diagnostic for CTE. Methods: Eight currently active professional male boxers aged 28 (mean) ± (SD) 6 years with clinical signs of mild CTE were compared to 12 activity-matched (non-boxer) controls (29 ± 5 years). The boxers included World, British and Commonwealth champions who had boxed 137 ± 97 professional rounds over 4-19 years. All boxers had a prior history of loss by technical or total knock-out. Transfer function analysis (TFA) of spontaneous oscillations in mean arterial pressure (MAP, finger photoplethysmography) and middle cerebral artery blood flow velocity (MCAv, trans-cranial Doppler ultrasound) in the low frequency (LF) range (0.07-0.20 Hz) was employed for the measurement of dCA (Zhang et al., 1998). Cerebrovascular resistance (CVR) was calculated as MAP/MCAv and cerebrovascular conductance (CVC) as MCAv/MAP. Following confirmation of distribution normality using Shapiro-Wilk W tests, data were analysed using independent samples t-tests. Results: The data presented in Table 1 identified that all aspects of cerebral haemodynamic function in boxers was comparable to that observed in controls with no evidence of any impairment. Furthermore, no differences were observed in TFA in either the very low and high frequency ranges.