Table 1

Crude slip incidence rates by group allocation and incidence rate ratios for the intervention group compared with the control group by age

Age group
(years)
Control groupIntervention groupIntervention relative to control group
NSlipsPerson-hoursCrude incidence rate* (95% CI)aIRR† (95% CI)NSlipsPerson- hoursCrude incidence rate* (95% CI)aIRR‡ (95% CI)P value
<30378721169 0910.160 (0.148 to 0.172)1.00 (ref)389641166 4750.144 (0.133 to 0.156)0.93 (0.73 to 1.20)0.585
30–39487919220 6390.156 (0.146 to 0.167)1.18 (0.94 to 1.48)475464209 9200.083 (0.076 to 0.091)0.58 (0.46 to 0.74)<0.001
40–496321218292 6660.156 (0.147 to 0.165)1.32 (1.06 to 1.64)616685277 1480.093 (0.086 to 0.100)0.53 (0.43 to 0.64)<0.001
50–596331023291 7990.131 (0.124 to 0.140)1.00 (0.80 to 1.25)677741306 8120.091 (0.084 to 0.097)0.69 (0.57 to 0.85)<0.001
60+11722950 9830.168 (0.147 to 0.192)2.00 (1.40 to 2.87)10010241 6030.092 (0.075 to 0.112)0.39 (0.24 to 0.64)<0.001
  • *Per 37.5 person-hours (also known as one full-time working week).

  • †aIRRs comparing age groups among the control group only, estimated using mixed-effects negative binomial regression with sex, prerandomisation slip rate and job role as fixed effects, and site as random effect.

  • ‡aIRRs comparing the intervention group to control group by age, estimated using mixed-effects negative binomial regression with sex, prerandomisation slip rate, job role, group allocation, and the interaction between group allocation and age as fixed effects, and site as random effect.

  • aIRR, adjusted incidence rate ratio; N, number of people; ref, reference category.