New and Recurrent Concussions in High-School Athletes Before and After Traumatic Brain Injury Laws, 2005-2016.

Objectives. To examine the trends of new and recurrent sports-related concussions in high-school athletes before and after youth sports traumatic brain injury laws. Methods. We used an interrupted time-series design and analyzed the concussion data (2005–2016) from High School Reporting Injury Online. We examined the trends of new or recurrent concussion rates among US representative high-school athletes partici- pating in 9 sports across prelaw, immediate-postlaw, and postlaw periods by using general linear models. We defined 1 athlete exposure as attending 1 competition or practice. Results. We included a total of 8043 reported concussions (88.7% new, 11.3% re- current). The average annual concussion rate was 39.8 per 100 000 athlete exposures. We observed significantly increased trends of reported new and recurrent concussions from the prelaw, through immediate-postlaw, into the postlaw period. However, the recurrent concussion rate showed a significant decline 2.6 years after the laws went into effect. Football exhibited different trends compared with other boys’ sports and girls’ sports. Conclusions. Observed trends of increased concussion rates are likely attributable to increased identification and reporting. Additional research is needed to evaluate intended long-term impact of traumatic brain injury laws