Rates of Concussion Are Lower in National Football League Games Played at Higher Altitudes

W hile concussions occur in nearly every sport and level of competition, the greatest frequency occurs in collision and contact sports such as football, lacrosse, hockey, rugby, soccer, and basketball.16,22,27 Specifically with regard to football, attempts at player-safety improvements for concussion prevention date back to the implementation of helmets by the National Football League (NFL) in 1943 and have continued virtually every year in the form of both rule changes and equipment modifications.32 Although scrutiny of sport-related concussion has only recently come to the public forefront, sustaining 1 or more of these concussive injuries presents a danger that has been a concern of the NFL for decades.6 With increased awareness of the rate of concussion injury and the potential detrimental long-term effects, the NFL has made efforts to identify the health consequences of repeated blows to the head while concurrently seeking to implement strategies that better protect the athletes from these injuries. In 2009, the league took a more aggressive stance on concussive events through the implementation of stricter guidelines for activities following postconcussion assessments. The postconcussion guidelines were revised and mandated that a player should not return to play if he exhibited any residual concussion symptoms (eg, loss of memory, headache, or dizziness) at rest T T STUDY DESIGN: Retrospective epidemiologic investigation.