Table 2.
Predictors of insulin sensitivity, disposition index, and metabolic risk in healthy nonobese children and adolescents
| Insulin sensitivity (WBISI) |
Disposition index |
Metabolic risk (metabolic Z score) |
||||
|---|---|---|---|---|---|---|
| Estimate (95% CI) | P | Estimate (95% CI) | P | Estimate (95% CI) | P | |
| SHBG (nmol/l) | 21.4% (7.9 to 35.7) | 0.001 | 14.1% (1.4 to 28.3) | 0.031 | −0.15 (−0.29 to −0.01) | 0.032 |
| Fat mass (kg) | −6.7% (−24.2 to 14.9) | 0.49 | 0.7% (−19.9 to 23.1) | 0.94 | 0.27 (0.01 to 0.53) | 0.041 |
| Vo2max (ml · kg−1 · min−1) | 38.5% (−12.3 to 120.4) | 0.16 | −5.4% (41.4 to 51.6) | 0.81 | −0.35 (−0.91 to 0.21) | 0.23 |
| Puberty† | 0.004 | 0.18 | 0.88 | |||
| Tanner II vs. I | −13.9% (−30.9 to 7.3) | −6.8% (25.9 to 17.4) | 0.07 (−0.20 to 0.34) | |||
| Tanner III vs. I | −26.7% (−42.9 to −5.8) | −4.9% (−26.7 to 23.4) | 0.14 (−0.17 to 0.45) | |||
| Tanner IV vs. I | −11.3% (−32.3 to 17.4) | 9.4% (−18.1 to 44.8) | 0.05 (−0.28 to 0.39) | |||
| Tanner V vs. I | 15.0% (−18.9 to 64.9) | 29.7% (−9.5 to 87.8) | 0.05 (−0.39 to 0.49) | |||
| Adjusted R2 | 0.48 | 0.04 | 0.38 | |||
Data are parameter estimates (95% CIs) for the continuous covariates. All models were adjusted for sex and age, none of which contributed significantly to any of the models. CIs are presented as the changes in the response resulting from a 100% increase in the covariate, i.e., a doubling of SHBG results in a 21.4% increase in WBISI and 0.15 SD reduction in the metabolic risk score. To calculate the change (d) in the dependent variable of a given change (c) in covariates, the following formulas can be used: for WBISI and disposition index (log-transformed), the change is d = clog2(Est). For the metabolic Z score (untransformed), the change is d = [Est/ln(2)] × ln(c). As an example, an isolated (i.e., not changing other covariates) 50% increase in SHBG levels will lead to a 12% [1.5log2(1.21) = 1.50.28] increase in WBISI and a 0.09 [(−0.15/ln(2)) × ln(1.5) = −0.22 × ln(1.5)] decrease in metabolic Z score. Significant P values (P < 0.05) are in boldface.
†For pubertal stages, the changes in relation to Tanner stage I are presented as relative changes for WBISI and disposition index and as absolute changes for metabolic Z score. As an example, the SHBG level is 26.7% lower and metabolic Z score 0.14 SD higher in Tanner stage III than in Tanner stage I.