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Table 2 Association of per cent density and dense area with age at menarche in pooled ICMD studies

From: The association of age at menarche and adult height with mammographic density in the International Consortium of Mammographic Density

  No. of women No. of measurements Per cent densitya Dense areaa, f
Changes in square-root per cent density (SE) P value Changes in square-root dense area (SE) P value
Age at menarche category (years)       
 < 12.0 1470 1722 0   0  
 12.0–12.9 2588 3036 0.006 (0.042) 0.889 − 0.032 (0.056) 0.575
 13.0–13.9 2594 3067 0.064 (0.042) 0.130 0.053 (0.056) 0.346
 14.0–14.9 2023 2397 0.057 (0.045) 0.207 0.034 (0.059) 0.569
 ≥ 15.0 2006 2364 0.128 (0.046) 0.005 0.166 (0.061) 0.007
Linear associations with a 1 year increase in age at menarche       
All women—Model Ac       
 All, BMI and height adjusted 10,681 12,586 0.023 (0.008) 0.003 0.032 (0.010) 0.002
 All, without BMI adjustment 10,681 12,586 0.057 (0.008) < 0.001 0.036 (0.010) 0.001
 All, without height adjustment 10,681 12,586 0.022 (0.008) 0.004 0.033 (0.010) 0.001
Subset by BMI group (kg/m2)       
 ≤ 20.0 652 752 0.037 (0.032) 0.251   N/Ab
 20.1–25.0 3915 4585 0.039 (0.013) 0.002 0.068 (0.014)  < 0.001
 25.1–30.0 3427 4048 0.013 (0.014) 0.328 0.005 (0.018) 0.782
 > 30.0 2687 3201 0.012 (0.016) 0.456 0.009 (0.023) 0.704
Pre-menopausal women—Model Bd       
 All 4349 5135 0.020 (0.013) 0.122 0.028 (0.017) 0.111
Subset by parity       
 Nulliparous women 483 558 − 0.044 (0.036) 0.226 0.009 (0.048) 0.847
 Parous women 3866 4577 0.027 (0.013) 0.045 0.026 (0.018) 0.162
 Parous women + age 1st birth adjustment 3866 4577 0.027 (0.013) 0.044 0.025 (0.018) 0.165
Post-menopausal women—Model Cd       
 All 5868 6902 0.022 (0.010) 0.029 0.029 (0.013) 0.029
 All + age at menopause adjustment 5868 6902 0.022 (0.010) 0.031 0.029 (0.013) 0.031
Subset by parity       
 Nulliparous women 535 626 0.005 (0.035) 0.891 0.022 (0.044) 0.623
 Parous women 5333 6276 0.023 (0.011) 0.029 0.029 (0.014) 0.040
 Parous women + age at 1st birth adjustment 5333 6276 0.021 (0.011) 0.051 0.026 (0.014) 0.064
 Parous women + age at menopause adjustment 5333 6276 0.023 (0.011) 0.030 0.029 (0.014) 0.041
 Parous women + ages at 1st birth + age at menopause adjustments 5333 6276 0.021 (0.011) 0.049 0.026 (0.014) 0.063
Nulliparous women—Model De       
 All 1068 1238 − 0.016 (0.025) 0.517 0.013 (0.033) 0.696
Parous women—Model Ec       
 All 9561 11,283 0.027 (0.008) 0.001 0.033 (0.011) 0.002
 All + age at 1st birth adjustment 9561 11,283 0.026 (0.008) 0.001 0.033 (0.011) 0.003
  1. BMI body mass index, ICMD International Consortium of Mammographic Density, SE standard error
  2. aA multi-level linear regression model was used to estimate the difference in square-root per cent density and dense area associated with each per year increase in age at menarche. Models specified correlations of women (level 1) within population groups (level 2)
  3. bBMI ≤ 20 category combined with BMI 20.1–25.0 categories due to lack of convergence
  4. cModels A (all women) and E (parous women): adjusted for age at mammogram3, menopausal status, age at mammogram*menopausal status interaction term, BMI3, use of HRT, mammogram view, calibration, reader, parity, height
  5. dModels B (pre-menopausal women) and C (post-menopausal women): adjusted for age at mammogram3, BMI3, use of HRT, mammogram view, calibration, reader, parity, height
  6. eModel D (nulliparous women): adjusted for age at mammogram3, menopausal status, age at mammogram* menopausal status interaction term, BMI3, use of HRT, mammogram view, calibration, reader, height
  7. fDense area models: BMI2 adjusted for instead of BMI3