Multivariable model: previous concussion history (PHC)
| Crude risk ratio (95% CI) | p value | Risk ratio adjusted for PHC* (95% CI) | p value | |
| Imputed participation exposure+imputed PA volume | 2.05 (1.40 to 3.01) | <0.001 | 2.17 (1.49 to 3.18) | <0.001 |
| Sensitivity analysis 5.1: imputed participation exposure+raw PA volume | 2.50 (1.54 to 4.08) | <0.001 | 2.65 (1.61 to 4.36) | <0.001 |
| Sensitivity analysis 5.2: raw participation exposure+imputed PA volume | 2.07 (1.41 to 3.04) | <0.001 | 2.18 (1.49 to 3.18) | <0.001 |
| Sensitivity analysis 5.3: raw participation exposure+raw PA volume | 2.52 (1.54 to 4.10) | <0.001 | 2.62 (1.59 to 4.34) | <0.001 |
Bolded=significant finding (ie, 95% CI do not cross 1.00).
Final model: log odds (number of concussions)=β0+β1(PA), adjusted for clustering by team and offset by participation hours.
*Thirty-six players who did not provide response regarding PHC were excluded.
PA, physical activity.