title: Effect of cognitive activity level on duration of post-concussion symptoms.
abstract: OBJECTIVE
  To determine the effect of cognitive activity level on duration of post-concussion symptoms.
  
  
  METHODS
  We conducted a prospective cohort study of patients who presented to a Sports Concussion Clinic within 3 weeks of injury between October 2009 and July 2011. At each visit, patients completed a scale that recorded their average level of cognitive activity since the previous visit. The product of cognitive activity level and days between visits (cognitive activity-days) was calculated and divided into quartiles. Kaplan-Meier Product Limit method was used to generate curves of symptom duration based on cognitive activity level. To adjust for other possible predictors of concussion recovery, we constructed a Cox proportional hazard model with cognitive activity-days as the main predictor.
  
  
  RESULTS
  Of the 335 patients included in the study, 62% were male, 19% reported a loss of consciousness, and 37% reported experiencing amnesia at the time of injury. The mean age of participants was 15 years (range, 8-23) and the mean number of previous concussions was 0.76; 39% of athletes had sustained a previous concussion. The mean Post-Concussion Symptom Scale score at the initial visit was 30 (SD, 26). The overall mean duration of symptoms was 43 days (SD, 53). Of all variables assessed, only total symptom burden at initial visit and cognitive activity level were independently associated with duration of symptoms.
  
  
  CONCLUSIONS
  Increased cognitive activity is associated with longer recovery from concussion. This study supports the use of cognitive rest and adds to the current consensus opinion.
authors.affiliation: Division of Sports Medicine, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania;
authors.forename: Naomi J
authors.initials: NJ
authors.lastname: Brown
authors.forename: Rebekah C
authors.initials: RC
authors.lastname: Mannix
authors.forename: Michael J
authors.initials: MJ
authors.lastname: O'Brien
authors.forename: David
authors.initials: D
authors.lastname: Gostine
authors.forename: Michael W
authors.initials: MW
authors.lastname: Collins
authors.forename: William P
authors.initials: WP
authors.lastname: Meehan
mesh_terms: D000293:Adolescent; D001265:Athletic Injuries / Q000523:psychology*; D002648:Child; D003071:Cognition; D005260:Female; D006801:Humans; D008297:Male; D038223:Post-Concussion Syndrome / Q000523:psychology*; D011446:Prospective Studies; D013997:Time Factors; D055815:Young Adult
keywords: concussion; mild traumatic brain injury; post-concussion syndrome; sports medicine