Objective Explore the correlation between number of head impacts sustained in amateur boxing sparring and expression of salivary microRNAs.

Design Observational, cross sectional study.

Setting Saliva samples collected immediately before and after bouts of sparring in elite male amateur boxers.

Participants 6 male amateur boxers, aged between 20 and 27 years.

Interventions (or Assessment of Risk Factors) Outcome Measures: Video footage of sessions was used to record number of punches and type of impact. Data on height, weight, career duration, number of career bouts and number of career rounds were collected. Difference in salivary miRNA expression between Pre and Post sparring samples were calculated as fold changes across 10 salivary microRNAs previously identified during the SCRUM study in professional rugby players.

Main Results No significant correlation was found between expression of any microRNA with height, weight, minutes of sparring completed, clean, body or hook type punches. Only hsa-miR-103a-3p showed a significant correlation with age (p=0.02, R=0.89). Significant correlations were found between hsa-miR-34b-3p and total hits to the head (HTH) (p=0.03, R=-0.86), total punches (p=0.02, R=-0.90) and HTH/min (p=0.02, R=-0.89). Hsa-miR-144–3p showed a significant correlation with HTH/min (p=0.05, R=0.89). Hsa-miR-135b-5p showed a significant correlation with total punches (p=0.05, R=-0.81).

Conclusions Change in microRNA expression of hsa-miR-34b-3p, hsa-miR-144–3p and hsa-miR-135b-5p correlate with increasing volumes of HTH. Further work to investigate levels of these markers in confirmed concussions in boxing and other sports is required to establish their potential utility as biomarkers of sport related concussion.