Table 4.
Regression models for LBP-related disability-free days and costs*
| Pain Free Days (N=389; R2=0.34) | Disability Free Days (N=389; R2=0.38) | Log Annual Cost of Treatment (N=388; R2=0.40) | Log Annual Cost of Treatment and Lost Productivity (N=388; R2=0.44) | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Regression Coefficient [95% CI] | P | Regression Coefficient [95% CI] | P | Regression Coefficient [95% CI] | P | Regression Coefficient [95% CI] | P |
| Intercept | 326.5 [241.5,411.6] | <.001 | 304.6 [231.4,377.9] | <.001 | 6.2 [4.3, 8.1] | <.001 | 6.0 [3.5, 8.5] | <.001 |
| Intervention (Reference category—SMT 0) | ||||||||
| SMT 6 | 16.8 [−3.9, 37.6] | 0.111 | 12.8 [−5.1, 30.6] | 0.160 | −0.1 [−0.6, 0.4] | .683 | 0.1 [−0.5, 0.7] | .649 |
| SMT 12 | 22.9 [1.8, 44.0] | 0.033 | 19.4 [ 1.3, 37.5] | 0.036 | 0.0 [−0.5, 0.5] | .936 | 0.2 [−0.5, 0.8] | .605 |
| SMT 18 | 18.4 [−2.3, 39.1] | 0.081 | 12.3 [−5.5, 30.1] | 0.174 | −0.1 [−0.6, 0.4] | .668 | −0.2 [−0.9, 0.4] | .428 |
| Socio-demographic | ||||||||
| Age | −0.2 [−0.7, 0.4] | 0.513 | −0.2 [−0.7, 0.3] | 0.367 | 0.0 [ 0.0, 0.0] | .020 | 0.0 [0.0, 0.0] | .611 |
| Male | 5.8 [9.4, 21.0] | 0.452 | 0.7 [−12.4, 13.8] | 0.918 | −0.2 [−0.6, 0.1] | .207 | −0.4 [−0.8, 0.1] | .086 |
| White non-Hispanic | −11.6 [−32.6, 9.5] | 0.281 | −3.5 [−21.6, 14.6] | 0.705 | 0.3 [−0.2, 0.8] | .196 | 0.0 [−0.6, 0.6] | .983 |
| Married | −4.4 [−21.1, 12.3] | 0.605 | 2.2 [−12.2, 16.6] | 0.761 | 0.1 [−0.2, 0.5] | .467 | 0.2 [−0.3, 0.7] | .362 |
| College-educated | −5.9 [−21.2, 9.4] | 0.447 | 1.5 [−11.6, 14.7] | 0.819 | 0.3 [ 0.1, 0.6] | .133 | 0.6 [−0.1, 1.0] | .016 |
| Low income (<$20,000) | −1.7 [−20.4, 16.9] | 0.855 | 1.3 [−14.7, 17.4] | 0.872 | 0.2 [−0.2, 0.6] | .370 | −0.1 [− 0.6, 0.5] | .766 |
| Smoker | −18.0 [−42.2, 6.2] | 0.145 | 3.1 [−23.9, 17.7] | 0.770 | 0.1 [−0.5, 0.6] | .786 | 0.0 [−0.7, 0.7] | .975 |
| Previous Treatment Experience | ||||||||
| Spinal Manipulation | 12.9 [−5.5, 31.3] | 0.168 | −2.2 [−18.0, 13.6] | 0.785 | 0.1 [−0.3, 0.5] | .608 | 0.3 [−0.3, 0.8] | .302 |
| Massage | −3.6 [−20.0, 12.9] | 0.669 | 2.8 [−11.4, 17.0] | 0.698 | 0.2 [−0.1, 0.6] | .228 | 0.5 [0.0, 1.0] | .036 |
| Confidence in Treatment | ||||||||
| SMT vs. massage (baseline) | 0.6 [−9.0, 10.2] | 0.900 | 3.5 [−4.7, 11.7] | 0.404 | 0.1 [−0.2, 0.3] | .631 | 0.0 [−0.2, 0.3] | .736 |
| Baseline health | ||||||||
| Pain (100-point scale) | −2.7 [−3.3, −2.0] | <.001 | −0.5 [−1.0, 0.1] | 0.083 | 0.0 [ 0.0, 0.0] | .125 | 0.0 [0.0, 0.0] | .206 |
| Disability (100-point scale) | −0.0 [−0.5, 0.5] | 0.943 | −1.4 [−1.8, −1.0] | <.001 | 0.0 [ 0.0, 0.0] | .005 | 0.0 [0.0, 0.0] | .102 |
| QALY (EQ-5D, range −0.109 to 1 | 106.9 [24.5,189.4] | 0.011 | 104.5 [33.5,175.5] | 0.004 | −3.3 [−5.1, −1.4] | .001 | −3.7 [−6.1, −1.3] | .003 |
| Costs (4 wks prior to enrollment) | ||||||||
| Treatment | N.A. | N.A. | 0.4 [ 0.3, 0.5] | <.001 | N.A. | |||
| Treatment & lost productivity | N.A. | N.A. | N.A. | 0.3 [0.2, 0.5] | <.001 | |||
N.A.-- Not Applicable.
*
Table 4 does not include study costs of study treatment as these are non-stochastic, additive, and could bias the multiplicative log model if included. There was no variability in study treatment costs. Note that study treatment costs are added into Table 5.