Table 4.
Sharing of genetic and environmental parameters between LDD and LBP: bivariate variance component analysis
| Parameter | LBP1* | LSUM | LBP_1Q |
|---|---|---|---|
| σAD2 | 0.399±0.049, h2=0.435† | 28.315±2.665, h2=0.682† | 3.608±0.288, h2=0.566† |
| σRS2 | 0.519±0.042 | 13.238±1.515 | 2.763±0.202 |
| α0 | −0.0763±0.0282 | −18.056±2.224 | −0.8557±0.3754 |
| βEXCERCISE | – | NS | 0.6919±0.1337 |
| βWEIGHT | – | 0.0859±0.0203 | 0.0276±0.0054 |
| βAGE | – | 0.4831±0.0326 | – |
| RAD | 0.3662±0.0842 (p<0.001) | 0.3318±0.0705 (p<0.001) | |
| RRS | 0.0910±0.080 (p=0.29) | 0.0815±0.0786 (p=0.41) |
LBP1 variable was adjusted using parameter estimates in multiple logistic regression (table 3), in which the contribution of the low back pain (LBP) status of twins was not included; Parameter estimates ± standard errors of estimates are provided in the table.
Contribution of the putative genetic effects (heritability estimate), adjusted for all significant covariates; σAD2, σRS2 are variance components attributable to genetic and random environmental effects on each variable separately; α0 and β are regression parameters, intercept and slope for the corresponding significant covariates; RAD and RRS are genetic and environmental correlations between LSUM and each of the two LBP variables respectively; p value in comparison with the corresponding general model in which all model parameters were estimated.
LDD, lumbar disc degeneration; LSUM, summary rank for four LDD traits.