Table 4
Results of the conventional and hierarchical analyses for the effect of the physical, psychosocial, and time related factors on incident LBP/D
| Conventional model RR (95%CI)* | Hierarchical model RR (95%CI) | ||
|---|---|---|---|
| *RR, relative risk; 95% CI, 95% confidence interval. | |||
| †pw = per week; ‡ct = centile of distribution; §() = actual value. | |||
| RRs (and 95% CI) are presented for the 25th, 50th, 75th, and 90th centile of the distribution in reference to the 10th centile. | |||
| Physical factors | |||
| Trunk flexion between 20° and 45° | 2 hours pw† | 1 reference | 1 reference |
| 3 hours pw | 0.83 (0.33 to 2.09) | 0.95 (0.53 to 1.72) | |
| 4 hours pw | 0.70 (0.12 to 4.20) | 0.90 (0.28 to 2.87) | |
| 5 hours pw | 0.60 (0.08 to 4.57) | 0.83 (0.22 to 3.18) | |
| 6 hours pw | 0.50 (0.07 to 3.72) | 0.80 (0.19 to 3.32) | |
| Trunk flexion over 45° | 30 minutes pw | 1 reference | 1 reference |
| 45 minutes pw | 1.56 (0.91 to 2.68) | 1.31 (1.03 to 1.65) | |
| 1 hour pw | 2.44 (0.83 to 7.16) | 1.71 (1.08 to 2.72) | |
| 1 hour 30 minutes pw | 6.49 (1.28 to 32.98) | 2.82 (1.16 to 6.86) | |
| 1 hour 45 minutes pw | 9.82 (2.05 to 47.10) | 3.18 (1.13 to 9.00) | |
| Lifting and carrying loads over 10 kg | 1 minute pw | 1 reference | 1 reference |
| 5 minutes pw | 1.02 (0.77 to 1.35) | 1.05 (0.94 to 1.17) | |
| 15 minutes pw | 1.08 (0.39 to 2.99) | 1.18 (0.79 to 1.77) | |
| 30 minutes pw | 0.71 (0.23 to 2.28) | 1.33 (0.60 to 2.95) | |
| 45 minutes pw | 1.03 (0.25 to 4.25) | 1.26 (0.38 to 4.20) | |
| Psychosocial factors | |||
| Decision authority | 10 ct‡ (13.3)§ | 1 reference | 1 reference |
| 25 ct (27.7) | 1.10 (0.66 to 1.86) | 1.07 (0.64 to 1.78) | |
| 50 ct (41.2) | 1.22 (0.45 to 3.32) | 1.13 (0.42 to 3.04) | |
| 75 ct (54.5) | 1.55 (0.56 to 4.34) | 1.50 (0.55 to 4.14) | |
| 90 ct (66.7) | 0.77 (0.21 to 2.82) | 0.76 (0.21 to 2.72) | |
| Skill discretion | 10 ct (16.0) | 1 reference | 1 reference |
| 25 ct (27.8) | 1.08 (0.62 to 1.88) | 1.10 (0.63 to 1.89) | |
| 50 ct (40.0) | 1.19 (0.44 to 3.26) | 1.22 (0.45 to 3.31) | |
| 75 ct (55.6) | 1.41 (0.51 to 3.90) | 1.44 (0.53 to 3.91) | |
| 90 ct (66.7) | 1.05 (0.36 to 3.09) | 1.09 (0.38 to 3.16) | |
| Work demands | 10 ct (27.0) | 1 reference | 1 reference |
| 25 ct (33.3) | 0.84 (0.60 to 1.19) | 0.86 (0.61 to 1.21) | |
| 50 ct (45.5) | 0.72 (0.32 to 1.67) | 0.75 (0.33 to 1.73) | |
| 75 ct (57.6) | 1.48 (0.65 to 3.36) | 1.41 (0.63 to 3.18) | |
| 90 ct (66.7) | 1.59 (0.65 to 3.90) | 1.45 (0.60 to 3.53) | |
| Time related factors | |||
| Age | 25 years | 1 reference | 1 reference |
| 30 years | 1.03 (0.74 to 1.43) | 1.01 (0.73 to 1.40) | |
| 40 years | 1.09 (0.40 to 2.93) | 1.03 (0.39 to 2.74) | |
| 50 years | 1.66 (0.56 to 4.93) | 1.49 (0.52 to 4.25) | |
| 55 years | 1.81 (0.59 to 5.53) | 1.68 (0.57 to 4.90) | |
| Years in service | 1 year | 1 reference | 1 reference |
| 5 years | 0.69 (0.33 to 1.45) | 0.70 (0.35 to 1.41) | |
| 10 years | 0.47 (0.19 to 1.17) | 0.45 (0.19 to 1.09) | |
| 15 years | 0.37 (0.12 to 1.09) | 0.34 (0.12 to 1.01) | |
| 20 years | 0.33 (0.11 to 1.03) | 0.32 (0.11 to 1.00) | |
