Epidemiology of Concussion in the National Football League, 2015-2019

Abstract

Background: Concussion in American football, and specifically the National Football League (NFL) is a major area of interest and key focus for injury prevention. Complete and accurate characterization of when, how, and to whom these injuries occur can facilitate injury reduction efforts. Existing studies of concussion in the NFL use publicly available data, potentially limiting data quality and the inferences that can be made.

Hypothesis: Concussion incidence in the NFL decreased across the 2015-2019 seasons.

Study design: Descriptive epidemiology study.

Level of evidence: Level 4.

Methods: Concussion incidence, including counts, one-season risk, and rates per game and player-plays, among active NFL players from 2015 to 2019 is described by year, season, play type, and roster position.

Results: A total 1302 concussions were identified from 2015 to 2019 among 1004 players. Of these, 80% occurred in NFL games. The average annual incidence of in-season game concussions changed over the study period, from 230.7 per season (2015-2017) to 177.0 per season (2018-2019); this represented a 23% decrease in game settings (P < 0.01). Practice concussions fluctuated across the years of the study from 38 to 67 per season (average = 50.8/season). There were 70.6 concussions per 100 preseason games, which was slightly higher than the regular season rate per game of 61.7. Overall, there were 790 regular season game concussions across 4,657,243 player-plays and 114,428 player-games during the 5-year study. In regular season games, the majority of concussions were sustained on running and passing plays (n = 119/season), and the highest average rate per play occurred on kickoffs (0.69/100 plays). Defensive secondary (cornerbacks, safeties, and generic defensive backs) and offensive line incurred the most concussions, and the highest rates of concussion were among tight ends and wide receivers.

Conclusion and relevance: Concussions in the NFL are a key focus for player safety. Concussion reduction strategies were implemented before 2018, after which there was a sustained 2-year decrease in concussion incidence, providing a new benchmark from which to work toward further injury reduction.

Keywords: American football; National Football League; concussion; epidemiology.

Figure 1.

Concussion Incidence in the National Football League, 2015-2019,^a as reported by medical staff to National Football League (NFL) electronic health records. Game concussion numbers decreased meaningfully in the last 2 years of the study period, reflecting a 23% decrease in average annual game concussion incidence. ^aThis figure includes only concussions that occurred during in-season NFL club practices and games. Offseason (n = 5 in 2015, n = 5 in 2016, n = 10 in 2017, n = 5 in 2018, n = 8 in 2019), conditioning (n = 1 in 2018 preseason), other team activities (n = 1 in 2017 preseason), and non-sport-related concussions are not shown. ^bAll postseason concussions occurred in games except for n = 1 in 2016 and n = 1 in 2019.

Figure 2.

Incidence of National Football League preseason and regular season game concussions, 2015-2019. Over the study period, multiple systematic changes were developed, initiated, and in some cases, enhanced in an attempt to better identify, diagnose, report, and reduce concussions. AT, athletic trainer; UNC, unaffiliated neurotrauma consultant; CMO, chief medical officer; EHR, electronic health record; IVRS, injury video review system. *The expected range for concussions was calculated using log-Poisson regression with generalized estimating equations to account for within-club correlations in observed injury rates per game. The range was computed using the 2015 through 2017 seasons compared with 2018.