title: Intraindividual cognitive variability before and after sports-related concussion.
abstract: OBJECTIVE
  Inconsistent performance is associated with cognitive dysfunction in a number of clinical populations. However, intraindividual cognitive variability in healthy individuals is poorly understood. Inconsistency poses a challenge to clinicians when interpreting change over time. This study examined intraindividual cognitive variability within a sample of college athletes tested at baseline and postconcussion.
  
  
  METHODS
  Athletes (n = 71) and control participants (n = 42) were tested with a comprehensive neuropsychological battery at baseline and postconcussion (athletes) or one month later (controls). A subset of indices with high internal consistency was used to calculate overall performance and performance variability. A k-means cluster analysis of baseline and postconcussion performance variability examined heterogeneity within the sample.
  
  
  RESULTS
  In the athlete sample, performance variability was significantly greater than zero, and was negatively correlated with overall performance at both time points (p < .001). Wechsler Test of Adult Reading Full Scale IQ estimate was significantly correlated with overall performance (p < .01), but not with performance variability. Cluster analysis revealed low-variability (n = 46) and high-variability (n = 25) cluster groups. Whereas the low-variability cluster group exhibited a pattern of performance similar to that of control participants, membership in the high-variability cluster group was associated with postconcussion cognitive dysfunction.
  
  
  CONCLUSIONS
  These findings suggest that normative cognitive performance in college athletes is characterized by significant intraindividual variation across tests. Cross-test intraindividual variability may impart clinically meaningful information, as higher levels of variability were related to poorer overall performance and postconcussion cognitive dysfunction.
authors.affiliation: Department of Neurosurgery.
authors.forename: Amanda R
authors.initials: AR
authors.lastname: Rabinowitz
authors.affiliation: Psychology Department.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Arnett
mesh_terms: D001245:Association Learning; D001265:Athletic Injuries / Q000150:complications*; D001924:Brain Concussion / Q000150:complications* / Q000209:etiology*; D016000:Cluster Analysis; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology*; D005260:Female; D006801:Humans; D007206:Individuality; D008297:Male; D009483:Neuropsychological Tests; D013334:Students; D014495:Universities