Brain function decline in healthy retired athletes who sustained their last sports concussion in early adulthood

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Abstract
Recent studies have shown that the detrimental effects of sports concussions on cognitive and motor function may persist up to a few years post-injury. The present study sought to investigate the effects of having sustained a sports concussion more than 30 years prior to testing on cognitive and motor functions. Nineteen healthy former athletes, in late adulthood (mean age = 60.79; SD = 5.16), who sustained their last sport-related concussion in early adulthood (mean age = 26.05; SD = 9.21) were compared with 21 healthy former athletes with no history of concussion (mean age = 58.89; SD = 9.07). Neuropsychological tests sensitive to age-related changes in cognition were administered. An auditory oddball paradigm was used to evoke P3a and P3b brain responses. Four TMS paradigms were employed to assess motor cortex excitability: (i) resting motor threshold; (ii) paired-pulse intracortical inhibition and intracortical facilitation; (iii) input/output curve and (iv) cortical silent period (CSP). A rapid alternating movement task was also used to characterize motor system dysfunctions. Relative to controls, former athletes with a history of concussion had: (i) lower performance on neuropsychological tests of episodic memory and response inhibition; (ii) significantly delayed and attenuated P3a/P3b components; (iii) significantly prolonged CSP and (iv) significantly reduced movement velocity (bradykinesia). The finding that the P3, the CSP as well as neuropsychological and motor indices were altered more than three decades post-concussion provides evidence for the chronicity of cognitive and motor system changes consecutive to sports concussion.