Evidence of reduced inhibition in older adults with a history of repetitive brain trauma. A transcranial magnetic stimulation study

Abstract International concern regarding the association between repetitive neurotrauma in sport and long term concerns with ageing continues. While previous studies have reported older (i.e. over 50 years) our study describes corticomotor changes across the lifespan between retired contact sport athletes, between the ages of 30 and 70 years. Retired athletes, minimum five years retired, (n=152; 48.6±9.0 years) and age-matched controls (n=72; 47.8±9.5 years) were assessed using single and paired-pulse transcranial magnetic stimulation (TMS) for active motor threshold (aMT), motor evoked potential and cortical silent period duration (expressed as MEP:cSP ratio), and short- and long-interval intracortical inhibition (SICI and LICI). Age-matched controls showed significant moderate correlations for MEP:cSP ratios at 130% ( rho =0.48), 150% ( rho =0.49)and 170% aMT ( rho =0.42; all p <0.001) and significant but small negative correlation for SICI ( rho =-0.27; p =0.030), and moderate negative correlation for LICI ( rho =-0.43; p <0.001). Further, group-wise correlation analysis shows significant stronger corelations (all p <0.05) in the control for each variable than in the retired players. This study is the first to characterise corticomotor differences between retired athletes and age matched controls across the lifespan. in those with a history of repetitive head trauma and provides a foundation for further work to utilise TMS as a prodromal marker useful in supplementing neuropsychological assessment for traumatic encephalopathy syndrome which currently lacks physiological biomarkers.