title: Concussion Incidence in Professional Football: Position-Specific Analysis With Use of a Novel Metric.
abstract: BACKGROUND
  In the United States alone, millions of athletes participate in sports with potential for head injury each year. Although poorly understood, possible long-term neurological consequences of repetitive sports-related concussions have received increased recognition and attention in recent years. A better understanding of the risk factors for concussion remains a public health priority. Despite the attention focused on mild traumatic brain injury (mTBI) in football, gaps remain in the understanding of the optimal methodology to determine concussion incidence and position-specific risk factors.
  
  
  OBJECTIVE
  To calculate the rates of concussion in professional football players using established and novel metrics on a group and position-specific basis.
  
  
  METHODS
  Case-control study; Level of evidence, 3.
  
  
  METHODS
  Athletes from the 2012-2013 and 2013-2014 National Football League (NFL) seasons were included in this analysis of publicly available data. Concussion incidence rates were analyzed using established (athlete exposure [AE], game position [GP]) and novel (position play [PP]) metrics cumulatively, by game unit and position type (offensive skill players and linemen, defensive skill players and linemen), and by position.
  
  
  RESULTS
  In 480 games, there were 292 concussions, resulting in 0.61 concussions per game (95% CI, 0.54-0.68), 6.61 concussions per 1000 AEs (95% CI, 5.85-7.37), 1.38 concussions per 100 GPs (95% CI, 1.22-1.54), and 0.17 concussions per 1000 PPs (95% CI, 0.15-0.19). Depending on the method of calculation, the relative order of at-risk positions changed. In addition, using the PP metric, offensive skill players had a significantly greater rate of concussion than offensive linemen, defensive skill players, and defensive linemen (P < .05).
  
  
  CONCLUSIONS
  For this study period, concussion incidence by position and unit varied depending on which metric was used. Compared with AE and GP, the PP metric found that the relative risk of concussion for offensive skill players was significantly greater than other position types. The strengths and limitations of various concussion incidence metrics need further evaluation.
  
  
  CONCLUSIONS
  A better understanding of the relative risks of the different positions/units is needed to help athletes, team personnel, and medical staff make optimal player safety decisions and enhance rules and equipment.
authors: Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors: John T
authors: JT
authors: Nathanson
authors: Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors: James G
authors: JG
authors: Connolly
authors: Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors: Frank
authors: F
authors: Yuk
authors: Concussion Management of New York, New York, New York, USA.
authors: Alex
authors: A
authors: Gometz
authors: Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors: Jonathan
authors: J
authors: Rasouli
authors: imPACT Applications, Inc, Pittsburgh, Pennsylvania, USA.
authors: Mark
authors: M
authors: Lovell
authors: Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors: Tanvir
authors: T
authors: Choudhri
keywords: National Football League; athlete exposures; concussion; concussion incidence; game positions; mTBI; position plays; risk assessment