Table 3

Rate ratios (RR) and their 95% CIs from univariate and multivariable regression models and sensitivity analysis modelling the rate of major slips

UnivariateMultivariable*Major slip
RR95% CIRR95% CIRR95% CI
Slip-resistant shoes0.370.26 to 0.530.460.34 to 0.630.600.24 to 1.48
Non slip-resistant shoes1.001.001.00
Mean coefficient of friction (0.1)0.660.54 to 0.820.790.66 to 0.950.460.31 to 0.66
Mean floor surface roughness, §
Ra (1 μm)1.040.87 to 1.25
Rpm (5 μm)0.990.81 to 1.21
Daily floor-cleaning frequency§0.880.79 to 0.99
  • * Adjusted for age, gender, BMI, education, primary language, job tenure and chain of the restaurants.

  • Model includes only coefficient of friction and shoes (not adjusted for age, gender, BMI, education, primary language, job tenure and chain of the restaurants).

  • Averaged coefficient of friction and surface roughness parameters at the restaurant level.

  • § Roughness parameters and floor-cleaning frequency not significant in the multivariable model and thus dropped from the model.

  • Floor surface roughness could not be measured in one location. Univariate rate ratios and 95% CIs based on data from 35 locations. Roughness parameters were dropped from the multivariable model, and analysis includes all 36 restaurants. Sensitivity analysis modelling major slips also includes 36 restaurants.