Results of the conventional and hierarchical analyses for the effect of the physical, psychosocial, and time related factors on incident LBP
| 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 | 1.25 (0.66 to 2.37) | 1.12 (0.71 to 1.77) | |
| 4 hours pw | 1.55 (0.44 to 5.37) | 1.25 (0.51 to 3.07) | |
| 5 hours pw | 1.55 (0.42 to 5.66) | 1.21 (0.45 to 3.30) | |
| 6 hours pw | 1.13 (0.30 to 4.22) | 0.91 (0.34 to 2.47) | |
| Trunk flexion over 45° | 30 minutes pw | 1 reference | 1 reference |
| 45 minutes pw | 0.99 (0.66 to 1.49) | 1.08 (0.90 to 1.30) | |
| 1 hour pw | 0.98 (0.43 to 2.23) | 1.16 (0.80 to 1.68) | |
| 1 hour 30 minutes pw | 1.31 (0.42 to 4.11) | 1.34 (0.66 to 2.74) | |
| 1 hour 45 minutes pw | 2.02 (0.60 to 6.83) | 1.40 (0.61 to 3.22) | |
| Lifting and carrying loads over 10 kg | 1 minute pw | 1 reference | 1 reference |
| 5 minutes pw | 1.01 (0.77 to 1.32) | 0.93 (0.85 to 1.02) | |
| 15 minutes pw | 1.03 (0.38 to 2.77) | 0.77 (0.54 to 1.08) | |
| 30 minutes pw | 0.54 (0.18 to 1.63) | 0.56 (0.28 to 1.11) | |
| 45 minutes pw | 0.33 (0.08 to 1.40) | 0.37 (0.13 to 1.09) | |
| Psychosocial factors | |||
| Decision authority | 10 ct‡ (13.3)§ | 1 reference | 1 reference |
| 25 ct (27.7) | 1.27 (0.80 to 2.03) | 1.25 (0.80 to 1.97) | |
| 50 ct (41.2) | 1.60 (0.65 to 3.95) | 1.54 (0.64 to 3.71) | |
| 75 ct (54.5) | 2.14 (0.84 to 5.40) | 2.03 (0.83 to 5.00) | |
| 90 ct (66.7) | 2.10 (0.74 to 6.00) | 1.91 (0.71 to 5.18) | |
| Skill discretion | 10 ct (16.0) | 1 reference | 1 reference |
| 25 ct (27.8) | 0.82 (0.53 to 1.28) | 0.81 (0.52 to 1.26) | |
| 50 ct (40.0) | 0.70 (0.31 to 1.56) | 0.69 (0.31 to 1.52) | |
| 75 ct (55.6) | 0.78 (0.36 to 1.67) | 0.77 (0.36 to 1.64) | |
| 90 ct (66.7) | 0.65 (0.26 to 1.62) | 0.67 (0.27 to 1.66) | |
| Work demands | 10 ct (27.0) | 1 reference | 1 reference |
| 25 ct (33.3) | 1.01 (0.76 to 1.36) | 1.03 (0.78 to 1.38) | |
| 50 ct (45.5) | 1.09 (0.53 to 2.23) | 1.14 (0.56 to 2.31) | |
| 75 ct (57.6) | 1.47 (0.71 to 3.05) | 1.47 (0.71 to 3.04) | |
| 90 ct (66.7) | 1.82 (0.76 to 4.39) | 1.78 (0.75 to 4.27) | |
| Time related factors | |||
| Age | 25 years | 1 reference | 1 reference |
| 30 years | 0.78 (0.57 to 1.05) | 0.80 (0.59 to 1.07) | |
| 40 years | 0.47 (0.19 to 1.16) | 0.51 (0.21 to 1.22) | |
| 50 years | 0.37 (0.14 to 0.95) | 0.38 (0.15 to 0.98) | |
| 55 years | 0.30 (0.11 to 0.82) | 0.33 (0.12 to 0.88) | |
| Years in service | 1 year | 1 reference | 1 reference |
| 5 years | 0.77 (0.41 to 1.45) | 0.78 (0.43 to 1.40) | |
| 10 years | 0.81 (0.36 to 1.80) | 0.79 (0.38 to 1.65) | |
| 15 years | 0.90 (0.35 to 2.32) | 0.85 (0.34 to 2.10) | |
| 20 years | 0.82 (0.30 to 2.23) | 0.79 (0.30 to 2.09) | |