Impaired cerebral haemodynamic function associated with chronic traumatic brain injury in professional boxers

The present study examined to what extent professional boxing compromises cerebral haemodynamic function and its association with CTBI (chronic traumatic brain injury). A total of 12 male professional boxers were compared with 12 age-, gender- and physical fitness-matched non-boxing controls. We assessed dCA (dynamic cerebral autoregulation; thigh-cuff technique and transfer function analysis), CVRCO2 (cerebrovascular reactivity to changes in CO2: 5% CO2 and controlled hyperventilation), orthostatic tolerance (supine to standing) and neurocognitivefunction (psychometric tests). Blood flow velocity in the middle cerebral artery (transcranial Doppler ultrasound),mean arterial blood pressure (finger photoplethysmography), end-tidal CO2 (capnography) and corticaloxyhaemoglobin concentration (near-IR spectroscopy) were continuously measured. Boxers were characterized byfronto-temporal neurocognitive dysfunction and impaired dCA as indicated by a lower rate of regulation andautoregulatory index (P<0.05 compared with controls). Likewise, CVRCO2 was also reduced resulting in a lowerCVRCO2 range (P<0.05 compared with controls). The latter was most marked in boxers with the highest CTBIscores and correlated against the volume and intensity of sparring during training (r= -0.84, P<0.05). Theseimpairments coincided with more marked orthostatic hypotension, cerebral hypoperfusion and corresponding cortical de-oxygenation during orthostatic stress (P<0.05 compared with controls). In conclusion, these findings provide the first comprehensive evidence for chronically impaired cerebral haemodynamic function in active boxersdue to the mechanical trauma incurred by repetitive, sub-concussive head impact incurred during sparring training. This may help explain why CTBI is a progressive disease that manifests beyond the active boxing career.