Objective there is currently limited information on the neurobiological effects of contact sport participation, and interactions with history of concussion. The goal of this study is to examine the interactions between history of concussion and contact sport participation, using biomarkers of cerebral metabolites, brain function, and white matter microstructure.

Design cross-sectional study.

Setting sport medicine clinic, affiliated with inter-university sport program (secondary care).

Participants 43 athletes without concussion in the past 6 months were recruited, including 22 athletes without prior concussion (13 non-contact, 9 contact; 11 female) and 21 athletes with a history of concussion (13 non-contact, 8 contact; 11 female).

Outcome measures Magnetic Resonance Imaging (MRI) was used to measure brain biomarkers: MRI spectroscopy to evaluate cerebral metabolites; functional MRI to assess brain function; diffusion tensor imaging for white matter microstructure.

Main results athletes in contact sports with prior concussion showed significant differences in brain structure and function, relative to athletes in non-contact sports, and those in contact sports without prior injury. This included significantly elevated glutamate ratios, decreased functional connectivity of the visual and motor systems, and increased fractional anisotropy of white matter.

Conclusions This study provides the first multi-modal MRI data showing altered brain structure and function in athletes with a history of concussion and interactions with contact sport participation. These findings provide strong preliminary evidence that athletes in contact sports may be more vulnerable to the long-term effects of sport concussion.

Competing interests None.