Table 2.
Yearly BSI rates by study phase. Adjusted rates were determined used generalised estimating equation (GEE) models for Poisson regression adjusted for age and school and accounting for within-subject correlation, using data across all phases of the study at once to make years comparable
| Phase | N | BSI events | Persons with BSI | Person-years | Crude rate | Adjusted rate | 95% CI |
| Historical | |||||||
| Year 1 | 35 | 18 | 18 | 29.9 | 0.60 | 0.59 | (0.39 to 0.91) |
| Year 2 | 36 | 14 | 11 | 32.1 | 0.44 | 0.42 | (0.22 to 0.77) |
| Year 3 | 31 | 16 | 10 | 28.1 | 0.57 | 0.57 | (0.31 to 1.02) |
| Total | 56 | 48 | 30 | 90.2 | 0.53 | 0.52 | (0.38 to 0.71) |
| Pilot | |||||||
| Year 1 | 30 | 5 | 4 | 28.6 | 0.18 | 0.19 | (0.08 to 0.45) |
| Year 2 | 34 | 19 | 14 | 29.8 | 0.64 | 0.59 | (0.36 to 0.97) |
| Year 3 | 44 | 19 | 17 | 36.8 | 0.52 | 0.48 | (0.30 to 0.75) |
| Total | 66 | 43 | 27 | 95.2 | 0.45 | 0.41 | (0.30 to 0.57) |
| Intervention* | |||||||
| Year 1 | 49 | 31 | 19 | 42.7 | 0.73 | 0.67 | (0.43 to 1.05) |
| Year 2 | 43 | 13 | 11 | 38.2 | 0.34 | 0.32 | (0.17 to 0.57) |
| Year 3 | 38 | 10 | 8 | 34.6 | 0.29 | 0.27 | (0.13 to 0.55) |
| Year 4 | 36 | 8 | 8 | 21.9 | 0.37 | 0.38 | (0.20 to 0.73) |
| Total | 78 | 62 | 34 | 137.3 | 0.45 | 0.43 | (0.31 to 0.59) |
*P value for historical versus intervention phase (derived from model that includes both phases plus age and school) = 0.34
BSI, bone stress injury .