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. The authors examined this relationship between concussion and batting performance among Major League Baseball (MLB) players. HYPOTHESIS Batting performance among concussed MLB players will be worse upon return to play than batting performance among players missing time for noninjury reasons. STUDY DESIGN Cohort study; Level of evidence, 3. METHODS The authors 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, they identified players who went on paternity or bereavement leave during the same period. Using repeated-measures generalized linear models, the authors compared 7 batting metrics between the 2 groups for the 2 weeks upon return, as well as 4 to 6 weeks after return, controlling for pre-leave batting metrics, number of days missed, and position. RESULTS The authors identified 66 concussions and 68 episodes of bereavement/paternity leave to include in the analysis. In the 2 weeks after return, batting average (.235 vs .266), on-base percentage (.294 vs .326), slugging percentage (.361 vs .423), and on-base plus slugging (.650 vs .749) were significantly lower among concussed players relative to the bereavement/paternity leave players (time×group interaction, P<.05). In weeks 4 to 6 after leave, these metrics were slightly lower in concussed players but not statistically significantly so. CONCLUSION Although concussed players may be asymptomatic upon return to play, the residual effects of concussion on the 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 and to identify better measures to use for return-to-play decisions.