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. Method: 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. Conclusion: 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.
