Table 2

Mean percentage of breast density, by IGF-I and IGFBP-3 quartiles (Q), among premenopausal women

Model covariatesMean percentage of breast density by IGF-I (ng/ml) quartilesSpearman correlation coefficienta (P)
Q1Q2Q3Q4
(85–134)(135–177)(178–212)(213–305)
Age and batch314235440.21 (0.11) 
Age, IGFBP-3, and batch294238440.27 (0.04) 
Age, IGFBP-3, alcohol intake, batch, and BMI303540440.36 (0.007)
Mean percentage of breast density by IGFBP-3 (ng/ml) quartiles
Q1Q2Q3Q4
(2090–3150)(3151–4000)(4001–4520)(4521–6670)
Age and batch44403139−0.10 (0.42) 
Age, IGF-I, and batch47392937−0.20 (0.12) 
Age, IGF-I, alcohol intake, batch, and BMI43443036−0.24 (0.07) 
Mean percentage of breast density by IGF-I: IGFBP-3 (molar ratio) quartiles
Q1Q2Q3Q4
(0.084–0.128)(0.129–0.162)(0.163–0.207)(0.208–0.367)
Age and batch303635520.34 (0.006)
Age, alcohol intake, batch, and BMI303338480.39 (0.004)
  • Spearman correlation between the continuous measure of percentage of breast density and the continuous level of IGF-I or IGFBP-3. Adjusted correlations are partial Spearman coefficients.