title: Effect of Concussion on Performance of National Football League Players.
abstract: OBJECTIVE
  Lingering neurologic injury after concussion may expose athletes to increased risk if return to play is premature. The authors explored whether on-field performance after concussion is a marker of lingering neurologic injury.
  
  
  METHODS
  Retrospective cohort study on 1882 skill-position players who played in the National Football League (NFL) during 2007-2010.
  
  
  METHODS
  Players with concussion based on the weekly injury report were compared with players with other head and neck injuries (controls) on measures of on-field performance using Football Outsiders' calculation of defense-adjusted yards above replacement (DYAR), a measure of a player's contribution controlling for game context. Changes in performance, relative to a player's baseline level of performance, were estimated before and after injury using fixed-effects models.
  
  
  RESULTS
  The study included 140 concussed players and 57 controls. Players with concussion performed no better or worse than their baseline on return to play. However, a decline in DYAR relative to their prior performance was noted 2 wk and 1 wk before appearing on the injury report. Concussed players performed slightly better than controls in situations where they returned to play the same week as appearing on the injury report.
  
  
  CONCLUSIONS
  On return, concussed NFL players performed at their baseline level of performance, suggesting that players have recovered from concussion. Decline in performance noted 2 wk and 1 wk before appearing on the injury report may suggest that concussion diagnosis was delayed or that concussion can be a multihit phenomenon. Athletic performance may be a novel tool for assessing concussion injury and recovery.
authors.forename: Nicole
authors.initials: N
authors.lastname: Reams
authors.forename: Rodney A
authors.initials: RA
authors.lastname: Hayward
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Kutcher
authors.forename: James F
authors.initials: JF
authors.lastname: Burke
mesh_terms: D054874:Athletic Performance / Q000502:physiology*; D001924:Brain Concussion / Q000175:diagnosis*; D005538:Football / Q000293:injuries* / Q000502:physiology; D006801:Humans; D012189:Retrospective Studies; D000068958:Return to Sport; D013997:Time Factors
keywords: American football; NFL; head injury