It is increasingly recognized that moderate to severe traumatic brain injury (TBI) (typically defined as loss of consciousness for >30 minutes1) increases the risk for dementia in older adulthood,2 a conclusion based primarily on epidemiologic research. Whether mild TBI, also called concussion, is associated with increased risk of dementia is less clear, especially because fewer prospective studies have focused on mild TBI.3 This is an important gap in the field, especially because concussion is relatively common, among both the general population and certain groups such as athletes and military service members.4 In recent years, concerns about potential for long-term negative consequences from concussion and even from subconcussive injuries have greatly intensified with the discovery of a distinct neuropathologic finding at autopsy among former US football players, other athletes, and military veterans exposed to repeated mild head injuries.5 This postmortem neuropathologic finding, which includes discovery of hyperphosphorylated τ in a characteristic cortical distribution, is now known as chronic traumatic encephalopathy (CTE).5 Although the clinical symptoms associated with CTE remain unclear, reports of deaths, including suicides of high-profile professional athletes later found to have CTE, have raised alarm about this condition and heightened fears about the potential risks of playing football and other contact sports.
Kaup AR, Yaffe K. Reassuring News About Football and Cognitive Decline? Not So Fast. JAMA Neurol. 2017;74(8):898–899. doi:10.1001/jamaneurol.2017.1324
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