A systematic review of potential long-term effects of sport-related concussion

Abstract

ObjectiveSystematic review of possible long-term effects of sports-related concussion in retired athletes.Data sourcesTen electronic databases.Study selectionOriginal research; incidence, risk factors or causation related to long-term mental health or neurological problems; individuals who have suffered a concussion; retired athletes as the subjects and possible long-term sequelae defined as >10 years after the injury.Data extractionStudy population, exposure/outcome measures, clinical data, neurological examination findings, cognitive assessment, neuroimaging findings and neuropathology results. Risk of bias and level of evidence were evaluated by two authors.ResultsFollowing review of 3819 studies, 47 met inclusion criteria. Some former athletes have depression and cognitive deficits later in life, and there is an association between these deficits and multiple prior concussions. Former athletes are not at increased risk for death by suicide (two studies). Former high school American football players do not appear to be at increased risk for later life neurodegenerative diseases (two studies). Some retired professional American football players may be at increased risk for diminishment in cognitive functioning or mild cognitive impairment (several studies), and neurodegenerative diseases (one study). Neuroimaging studies show modest evidence of macrostructural, microstructural, functional and neurochemical changes in some athletes.ConclusionMultiple concussions appear to be a risk factor for cognitive impairment and mental health problems in some individuals. More research is needed to better understand the prevalence of chronic traumatic encephalopathy and other neurological conditions and diseases, and the extent to which they are related to concussions and/or repetitive neurotrauma sustained in sports.

Dietary Energy Restriction Ameliorates Cognitive Impairment in a Mouse Model of Traumatic Brain Injury

“…TBI is a common cause of enduring cognitive deficits and behavioral alterations in the general public, contact sport athletes, and military personnel (Bogdanova and Verfaellie 2012; Manley et al 2017). Moreover, while mTBI may not cause overt neuronal degeneration in the short-term, repeated concussions can result in a delayed progressive neurodegenerative process called chronic traumatic encephalopathy (Vos et al 2018).…”

American Medical Society for Sports Medicine position statement on concussion in sport

“…Subconcussive impacts are defined as transfer of mechanical energy to the brain causing presumed axonal or neuronal injury in the absence of clinical signs or symptoms 112. It is unclear if a biomechanical threshold or other factors lead to injury or if this entity qualifies as injury since it does not seem to be associated with neuropsychological changes 113.…”

Sports Concussion: A Clinical Overview

“…Repetitive neurotrauma sustained during a career in boxing has been reported to be associated with chronic brain damage in some former athletes since the 1920s [103], but it has only been associated with former National Football League (NFL) players more recently. A review on this issue conducted by Manley and colleagues [104] reported that there is emerging evidence that some retired NFL players have mild cognitive impairment [105,106], neuroimaging abnormalities [107,108], and differences in brain metabolism [109] [8]. An initial period of 24-48 hours of both relative physical rest and cognitive rest is recommended before commencing the GRTP process.…”

“…For a comprehensive review of this literature see Manley et al [104], Iverson et al [111], Gardner et al [112], Randolph et al [113], and McCrory et al [114].…”