Concussions are associated with decreased batting performance among Major League Baseball Players

Background: Concussions impair balance, visual acuity and reaction time, all of which are required for high-level batting performance, but the effects of concussion on batting performance have not been reported. We examined this relationship between concussion and batting performance among Major League Baseball (MLB) Players.

Methods: We identified MLB players who sustained a concussion between 2007 and 2013 through league disabled list records and a Baseball Prospectus database. For a comparison group, we identified players who went on paternity or bereavement leave during the same period. Using repeated-measures ANCOVAs, we compared seven batting metrics between the two groups for the two weeks upon return, as well as 4-6 weeks after return, controlling for pre-leave batting metrics, number of days missed, and position.

Results: We identified 59 concussions and 63 episodes of paternity/bereavement leave to include in the analysis. In the 2 weeks following return, batting average (.234 vs .264), slugging percentage (.359 vs .420), and on-base plus slugging (.654 vs .747) were significantly lower among concussed players relative to the paternity/bereavement leave players (p<0.05). During weeks 4-6 following leave, these metrics remained lower in concussed players, but not statistically significantly so; however, home run percentage was significantly lower among concussed players (1.4% vs. 3.3%; p<0.05).

Conclusions: Although concussed players may be asymptomatic upon return to play, the residual effects of concussion on the complex motor skills required for batting may still be present. Further work is needed to clarify the mechanism through which batting performance after concussion is adversely affected.