Table 2. Regression coefficienta (95% confidence intervals) for percent breast density by calcium and vitamin D intake at the age of 53 years separately for pre-menopausal and post-menopausal women at the time of mammographyb.
|
Pre-menopausal at the time of mammography (n=121)
|
Post-menopausal at the time of mammography (n=166)
|
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|---|---|---|---|---|---|---|
| N | Median percent breast density (IQR range)c | Regression coefficient (95% CI) | N | Median percent breast density (IQR range)c | Regression coefficient (95% CI) | |
| Age 53 years | ||||||
| Calcium intake (mg day−1) | ||||||
| ⩽699 | 18 | 26.5 (18.3) | Reference | 30 | 22.2 (19.6) | Reference |
| 700–846 | 21 | 26.1 (38.7) | 0.14 (−0.55, 0.82) | 32 | 19.9 (25.5) | −0.11 (−0.55, 0.33) |
| 847–976 | 25 | 30.2 (26.6) | 0.03 (−0.63, 0.69) | 30 | 18.9 (23.2) | −0.31 (−0.77, 0.15) |
| 977–1179 | 23 | 27.0 (28.9) | 0.03 (−0.63, 0.69) | 35 | 14.8 (29.2) | −0.64 (−1.09 −0.19) |
| ⩾1180 | 34 | 31.0 (33.1) | 0.37 (−0.32, 1.04) | 39 | 20.9 (23.9) | −0.53 (−1.02, −0.03) |
| P-value for linear trend | 0.4 | 0.006 | ||||
| Per 1 s.d. increase in calcium intake | 0.10 (−0.12, 0.33) | −0.12 (−0.25, 0.02) | ||||
| Vitamin D intake (μg day−1) | ||||||
| ⩽2.198 | 26 | 26.8 (30.6) | Reference | 32 | 19.1 (25.2) | Reference |
| 2.199–3.118 | 29 | 28.6 (23.4) | 0.29 (−0.28, 0.86) | 32 | 21.8 (30.4) | −0.06 (−0.48, 0.36) |
| 3.119–4.702 | 22 | 19.5 (27.5) | 0.09 (−0.52, 0.69) | 32 | 20.6 (21.5) | 0.09 (−0.33, 0.53) |
| 4.702–7.841 | 21 | 27.6 (44.0) | 0.37 (−0.23, 0.97) | 38 | 15.1 (20.4) | −0.11 (−0.52, 0.31) |
| ⩾7.842 | 23 | 33.7 (38.6) | 0.30 (−0.27, 0.87) | 32 | 21.7 (24.1) | 0.10 (−0.36, 0.55) |
| P-value for linear trend | 0.3 | 0.5 | ||||
| Per 1 s.d. increase in vitamin D intake | −0.05 (−0.17, 0.28) | 0.05 (−0.15, 0.26) | ||||
a
Adjusted for mammographic view (cranio-caudal and medio-lateral oblique), age at the time of mammogram (continuous), BMI at the age of 53 years (continuous), total energy intake (continuous), age at menarche (<12, 12, 13 and 14+ years), parity (0, 1, 2, 3 and 4+), smoking status (current smoker and non-smoker) and social class during adult life (non-manual and manual).
b
Excludes women who were peri-menopausal (n=120), underwent a surgical menopause (n=116), on HT (139) or whose menopausal status was unknown (n=12).
c
Inter-quartile range.