On-field Head Acceleration Exposure Measurement Using Instrumented Mouthguards: Missing Data Imputation for Complete Exposure Analysis.

Purpose: Accurate quantification of head acceleration event (HAE) exposure is critical for investigating brain injury risk in contact sports athletes. However, missing HAEs may be unavoidable in real-world data collection. This study introduces missing data imputation methods to estimate complete video- and sensor-based HAE exposure.

Methods: We captured and verified university men's ice hockey HAEs using video and instrumented mouthguards (iMGs) in one varsity season (n = 27, n = 31). A statistical mapping technique was first introduced to impute missing video-based HAEs during away games with limited camera angles. We then applied multiple imputation to impute missing iMG-based HAEs using captured data, including the complete video-based HAE exposure. This enabled estimation of complete exposure data at a per-athlete level over all games of the season.

Results: Among 591 athlete-games, 45% did not have any recorded iMG data. We find that data imputation increased the median values of per-athlete-season video- and iMG-based HAE counts by 10% and 69%, respectively. Consequently, common head kinematics- and brain deformation-based cumulative exposure metrics also increased substantially (median per-athlete-season cumulative peak linear acceleration by 95%, peak angular acceleration by 109%, and corpus callosum strain by 69%).

Conclusion: This study highlights the potential underestimation of exposure metrics due to missing HAEs and fills a critical gap in sports HAE exposure research. Future studies should incorporate missing data imputation methods for more accurate estimation of HAE exposure in investigating acute and long-term brain trauma risks.