TABLE 1.

Definitions of Main Outcomes of Interest, Accompanied by Estimated Measures of Interest, Comparisons Made, and Statistical Analyses Used for Examinations of Concussions Among High School Athletes in 20 Sports, 2013/14-2017/18 Academic Years

Outcome	Definition	Measure of interest
Symptom presentation	A list of symptoms (amnesia, difficulty concentrating, confusion/disorientation, dizziness/unsteadiness, headache, hyperexcitability, irritability, loss of consciousness, nausea, tinnitus, light sensitivity, noise sensitivity, foggy, and potential ‘other’ symptoms) were evaluated for all SRCs (dichotomized as yes/no). Multiple symptoms could be reported for each SRC. As clinicians were presented with the aforementioned subset of options for symptom selection, all reported concussions were retained for analysis even if no associated symptoms were reported	Calculated as the proportion of SRCs reported with a given symptom among all SRCs
Symptom count	Overall count of symptoms reported (from 15 symptoms options)	Discrete symptom count
Symptom Resolution Time (SRT)	The time between when the athlete first reported concussion symptoms and when all assessed concussion symptoms had dissipated (ordinally recorded within HS RIOTM)	Proportions of SRCs with values of SRT <7 and >21 d (SRT was recorded as less than 15 min, 15-29 min, 30-59 min, 1-11 h, 12-23 h, 1-2 d, 3-6 d, 7-9 d, 10-21 d, 22 d or more, within the surveillance system. Categories were combined for analysis)
Return-to-play time (RTP)	Defined as the number of days between injury and return to activity at a level that would allow competition (ordinally recorded within HS RIOTM)	Proportions of SRCs with values of RTP <7 and >21 d. For RTP >21 d, SRCs that resulted in a medical disqualification (for the season or career) were included. (RTP was recorded as less than 1, 1-2, 3-6, 7-9, 10-21, 22 d or more, medical disqualification for season, medical disqualification for career, athlete chooses not to continue, athlete released from team (no medical disqualification), season ended before athlete returned to activity, within the surveillance system. Categories were combined for analysis)