title: Cumulative effects of concussion in high school athletes.
abstract: OBJECTIVE
  A common assumption in sports medicine is that a history of concussion is predictive of a lower threshold for, as well as a worse outcome after, subsequent concussive injury. The current study was conducted to investigate the relationship between concussion history in high school athletes and the on-field presentation of symptoms after subsequent concussion.
  
  
  METHODS
  One hundred seventy-three athletes who experienced sports-related concussion composed the initial study group. Binary groups were subsequently created on the basis of concussion history. Sixty athletes with no concussion history were compared with 28 athletes with a history of three or more concussions. The groups were compared in terms of the on-field presentation of symptoms after an in-study concussion. Dependent variables included the postinjury presence of loss of consciousness, anterograde amnesia, retrograde amnesia, and confusion.
  
  
  RESULTS
  Athletes with three or more prior concussions were more likely to experience on-field positive loss of consciousness (chi(2) = 8.0, P = 0.005), anterograde amnesia (chi(2) = 5.5, P = 0.019), and confusion (chi(2) = 5.1, P = 0.024) after a subsequent cerebral concussion. An odds ratio revealed that athletes with a history of three concussions were 9.3 times more likely than athletes with no history of concussion to demonstrate three to four abnormal on-field markers of concussion severity.
  
  
  CONCLUSIONS
  This study is the first to suggest a cumulative effect of concussion in high school athletes. A more severe on-field presentation of concussion markers is evidenced in high school athletes with a pronounced history of concussion. This study's findings highlight the need for more long-term outcome studies in high school athletes who sustain sports-related concussions.
authors.affiliation: Department of Orthopaedic Surgery, Sports Medicine Concussion Program, University of Pittsburgh Medical Center, 3200 S. Water Street, Pittsburgh, PA 15203, USA. collinsmw@msx.upmc.edu
authors.forename: Michael W
authors.initials: MW
authors.lastname: Collins
authors.forename: Mark R
authors.initials: MR
authors.lastname: Lovell
authors.forename: Grant L
authors.initials: GL
authors.lastname: Iverson
authors.forename: Robert C
authors.initials: RC
authors.lastname: Cantu
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Maroon
authors.forename: Melvin
authors.initials: M
authors.lastname: Field
mesh_terms: D000293:Adolescent; D000647:Amnesia / Q000209:etiology; D001265:Athletic Injuries / Q000503:physiopathology*; D001924:Brain Concussion / Q000150:complications / Q000503:physiopathology* / Q000523:psychology; D003221:Confusion / Q000209:etiology; D004198:Disease Susceptibility; D005260:Female; D006801:Humans; D008297:Male; D012008:Recurrence; D012574:Schools; D015599:Trauma Severity Indices; D014474:Unconsciousness / Q000209:etiology