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. 2012 Apr 6;97(6):2068–2076. doi: 10.1210/jc.2011-2721

Table 3.

Multivariable associations of fat mass and markers of insulin resistance with BMD at age 15–16 yr (n = 2305)

Exposurea Mean difference in BMD (g/cm2) per 1-sd of exposure (95% confidence interval)
Model 1
 Model 2
 Model 3
Males, n = 1100 Females, n = 1205 P interactionb Males, n = 1100 Females, n = 1205 P interactionb Males, n = 1100 Females, n = 1205 P interactionb
Fat mass 0.017 (0.012, 0.022) 0.030 (0.026, 0.034) 0.01 0.017 (0.012, 0.022) 0.027 (0.024, 0.032) 0.04 0.019 (0.013, 0.025) 0.028 (0.024, 0.033) 0.08
    P value <0.001 <0.001 <0.001 <0.001 <0.001 <0.001
Insulin 0.002 (−0.003, 0.009) 0.006 (0.002, 0.010) 0.23 0.002 (−0.003, 0.007) 0.005 (0.001, 0.009) 0.48 −0.007 (−0.012, −0.002) −0.004 (−0.008, 0.000) 0.64
    P value 0.57 0.007 0.38 0.03 0.003 0.05
Glucose −0.002 (−0.008, 0.002) −0.002 (−0.006, 0.003) 0.75 −0.001 (−0.006, 0.004) −0.001 (−0.005, 0.003) 0.85 −0.003 (−0.008, 0.002) 0.000 (−0.004, 0.003) 0.51
    P value 0.49 0.41 0.73 0.57 0.21 0.93
Triglycerides 0.004 (0.001, 0.010) −0.001 (−0.005, 0.003) 0.14 0.003 (−0.002, 0.009) −0.001 (−0.005, 0.003) 0.12 0.000 (−0.004, 0.005) −0.001 (−0.005, 0.003) 0.61
    P value 0.04 0.33 0.09 0.22 0.84 0.62
HDLc −0.016 (−0.021, −0.011) −0.008 (−0.012, −0.004) 0.03 −0.013 (−0.018, −0.008) −0.008 (−0.012, −0.004) 0.06 −0.005 (−0.010, 0.000) −0.002 (−0.006, 0.001) 0.41
    P value <0.001 <0.001 <0.001 <0.001 0.01 0.23

Results are mean difference in BMD (grams per square centimeter) per 1-sd greater exposure value (95% confidence intervals) and P value. Model 1 controls for age by standardizing exposure on age and is adjusted for height and height squared in models with fat mass as exposure. Model 2 is the same as model 1 plus additional adjustment for confounders head of household social class, maternal and paternal education, ethnicity, maternal and paternal smoking, pubertal stage, and age of menarche (females). Model 3 assesses whether indicators of insulin resistance (insulin, glucose, triglyceride, and HDLc) mediate associations of fat mass and for other exposures whether fat mass confounds their association with outcomes. This model is identical to model 2 but also adjusts fat mass for all other exposures listed in the first column and adjusts each of these exposures for fat mass (height and height squared).

a

All exposures are age-standardized sd (z-) scores; hence, outcomes are mean difference per 1-sd exposure.

b

P interaction tests the null hypothesis that the association in males and females is the same.