Concussion | Concussion >10 days of time-loss | |||||
BC experience (years) | 0 | 1 | 2+ | 0 | 1 | 2+ |
No. of player-seasons | 557 | 651 | 634 | 557 | 651 | 634 |
No. of concussions | 64 | 61 | 49 | 34 | 33 | 30 |
Player participation (game-hours) | 16 237.48 | 15 997.68 | 17 496.32 | 16 237.48 | 15 997.68 | 17 496.32 |
Concussion rate, injuries per 1000 player game-hours (95% CI)* | 3.94 (3.03 to 5.11) | 3.81 (2.83 to 5.13) | 2.80 (1.90 to 4.13) | 2.09 (1.52 to 2.88) | 2.06 (1.42 to 3.00) | 1.71 (1.09 to 2.70) |
IRR (95% CI)† | 1 (reference) | 0.98 (0.67 to 1.44) | 0.81 (0.54 to 1.21) | 1 (reference) | 1.01 (0.62 to 1.67) | 0.88 (0.53 to 1.47) |
Absolute risk reduction, injuries per 1000 player game-hours (95% CI) | 1 (reference) | 0.13 (−1.38 to 1.63) | 1.14 (−0.30 to 2.59) | 1 (reference) | 0.03 (−1.04 to 1.10) | 0.38 (−0.62 to 1.37) |
*Crude rates with 95% Poisson CIs adjusted for cluster by team (offset by game-hours).
†IRRs and corresponding 95% CI based on multilevel Poisson regression with one random effect at the team level (offset by game-hours).
BC, body checking; IRR, incidence rate ratio.