title: A prospective study of concussions among National Hockey League players during regular season games: the NHL-NHLPA Concussion Program.
abstract: BACKGROUND
  In 1997, the National Hockey League (NHL) and NHL Players' Association (NHLPA) launched a concussion program to improve the understanding of this injury. We explored initial postconcussion signs, symptoms, physical examination findings and time loss (i.e., time between the injury and medical clearance by the physician to return to competitive play), experienced by male professional ice-hockey players, and assessed the utility of initial postconcussion clinical manifestations in predicting time loss among hockey players.
  
  
  METHODS
  We conducted a prospective case series of concussions over seven NHL regular seasons (1997-2004) using an inclusive cohort of players. The primary outcome was concussion and the secondary outcome was time loss. NHL team physicians documented post-concussion clinical manifestations and recorded the date when a player was medically cleared to return to play.
  
  
  RESULTS
  Team physicians reported 559 concussions during regular season games. The estimated incidence was 1.8 concussions per 1000 player-hours. The most common postconcussion symptom was headache (71%). On average, time loss (in days) increased 2.25 times (95% confidence interval [CI] 1.41-3.62) for every subsequent (i.e., recurrent) concussion sustained during the study period. Controlling for age and position, significant predictors of time loss were postconcussion headache (p < 0.001), low energy or fatigue (p = 0.01), amnesia (p = 0.02) and abnormal neurologic examination (p = 0.01). Using a previously suggested time loss cut-point of 10 days, headache (odds ratio [OR] 2.17, 95% CI 1.33-3.54) and low energy or fatigue (OR 1.72, 95% CI 1.04-2.85) were significant predictors of time loss of more than 10 days.
  
  
  CONCLUSIONS
  Postconcussion headache, low energy or fatigue, amnesia and abnormal neurologic examination were significant predictors of time loss among professional hockey players.
authors.affiliation: Sport Medicine Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alta. bbenson@ucalgary.ca
authors.forename: Brian W
authors.initials: BW
authors.lastname: Benson
authors.forename: Willem H
authors.initials: WH
authors.lastname: Meeuwisse
authors.forename: John
authors.initials: J
authors.lastname: Rizos
authors.forename: Jian
authors.initials: J
authors.lastname: Kang
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Burke
mesh_terms: D000293:Adolescent; D000328:Adult; D001924:Brain Concussion / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D002170:Canada / Q000453:epidemiology; D006688:Hockey / Q000293:injuries*; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D011446:Prospective Studies; D018582:Sick Leave / Q000706:statistics & numerical data; D018709:Statistics, Nonparametric; D055815:Young Adult