Comparison of trends in mean change in percent mammographic breast density after the one-year intervention among arms receiving vitamin D3 or placebo, according to baseline characteristics
| Vitamin D3 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Placebo | 1,000 IU/day | 2,000 IU/day | 3,000 IU/day | Linear trend in change in percent densityb | Interactionb | ||||||
| Baseline characteristics | N | Change in densitya | N | Change in densitya | N | Change in densitya | N | Change in densitya | ß (95% CI) | P | P |
| Serum 25(OH)D3c | |||||||||||
| <50 nmol/L | 19 | –5.4 ± 1.2 | 24 | –5.6 ± 1.1 | 27 | –4.9 ± 1.0 | 32 | –4.0 ± 0.9 | 0.53 (–0.40–1.46) | 0.27 | 0.99 |
| ≥50 nmol/L | 77 | –5.8 ± 0.6 | 72 | –5.4 ± 0.6 | 72 | –6.2 ± 0.6 | 68 | –3.8 ± 0.6 | 0.52 (–0.02–1.06) | 0.06 | |
| Body mass index | |||||||||||
| <25 kg/m2 | 62 | –6.5 ± 0.7 | 59 | –6.0 ± 0.7 | 63 | –6.0 ± 0.6 | 73 | –4.6 ± 0.6 | 0.59 (0.03–1.14) | 0.04 | 0.95 |
| ≥25 kg/m2 | 34 | –4.3 ± 0.9 | 37 | –4.5 ± 0.8 | 36 | –5.6 ± 0.9 | 27 | –1.7 ± 1.0 | 0.55 (–0.26–1.37) | 0.18 | |
| Total calcium intaked | |||||||||||
| <1,000 mg/day | 57 | –5.8 ± 0.7 | 44 | –5.4 ± 0.8 | 48 | –6.0 ± 0.8 | 50 | –3.8 ± 0.7 | 0.55 (–0.08–1.19) | 0.09 | 0.92 |
| ≥1,000 mg/day | 38 | –5.8 ± 0.8 | 49 | –5.6 ± 0.7 | 47 | –5.9 ± 0.8 | 47 | –3.8 ± 0.8 | 0.60 (–0.10–1.30) | 0.09 | |
| Percent breast density | |||||||||||
| <40% | 55 | –3.9 ± 0.7 | 52 | –4.0 ± 0.7 | 64 | –5.2 ± 0.6 | 61 | –2.6 ± 0.6 | 0.29 (–0.29–0.87) | 0.32 | 0.36 |
| ≥40% | 41 | –8.3 ± 0.8 | 44 | –7.1 ± 0.7 | 35 | –7.0 ± 0.8 | 39 | –5.9 ± 0.8 | 0.72 (0.02–1.42) | 0.04 | |
| Month of mammography | |||||||||||
| October–February | 40 | –4.7 ± 0.8 | 40 | –4.8 ± 0.8 | 37 | –5.6 ± 0.9 | 39 | –3.2 ± 0.8 | 0.34 (–0.38–1.07) | 0.35 | 0.48 |
| March–September | 56 | –6.5 ± 0.7 | 56 | –5.9 ± 0.7 | 62 | –6.0 ± 0.7 | 61 | –4.2 ± 0.7 | 0.68 (0.08–1.28) | 0.03 | |
| Type of mammography | |||||||||||
| CR | 53 | –6.4 ± 0.7 | 50 | –5.3 ± 0.8 | 49 | –5.4 ± 0.8 | 52 | –3.4 ± 0.8 | 0.90 (0.27–1.53) | 0.006 | 0.10 |
| DR | 43 | –4.9 ± 0.8 | 46 | –5.6 ± 0.8 | 50 | –6.3 ± 0.8 | 48 | –4.3 ± 0.8 | 0.11 (–0.56–0.79) | 0.74 | |
↵aMean ± SE of the difference between percent mammographic breast density at the end of the one-year intervention and that at baseline.
↵bß (95% confidence intervals) and P values for trend in mean change in mammographic breast density, and Pinteraction, are estimated from regression models. Study arm is treated as a continuous variable, and ß represents mean difference in change in percent mammographic breast density for increments of 1,000 IU/day vitamin D3. Models are adjusted for sites.
↵cMedian serum 25(OH)D3 was 39 nmol/L in the subgroup with baseline 25(OH)D3 <50 nmol/L, and 69 nmol/L in that with baseline 25(OH)D3 ≥ 50 nmol/L.
↵dAmong women who completed the C-DHQ1 at baseline (n = 380).