Table 3.

Comparisons of change in percent mammographic breast density after the one-year intervention between arms receiving vitamin D3 with placebo

Vitamin D3
Placebo1,000 IU/day2,000 IU/day3,000 IU/dayLinear trend in change in percent densityd
Comparisons of percent density(n = 96)(n = 96)(n = 99)(n = 100)ß (95% CI)P
Percent density at baseline (mean ± SD)40.0 ± 16.538.2 ± 14.937.3 ± 15.138.5 ± 16.6
Percent density at end of intervention (mean ± SD)a34.2 ± 14.932.8 ± 14.231.5 ± 14.234.7 ± 15.7
Change in percent densityb (mean ± SE)–5.7 ± 0.5–5.5 ± 0.5–5.9 ± 0.5–3.8 ± 0.5
Difference from placeboc0.00.3–0.11.90.53 (0.07–0.99)0.02
 (95% CI)c(–1.5–2.1)(–1.9–1.7)(0.1–3.7)
Pc1.01.00.03
  • aThe Pearson correlation coefficient between percent mammographic density at baseline and at the end of the one-year intervention in each of the four study arms ranges between 0.94 and 0.95.

  • bMean ± SE changes between percent mammographic breast density at the end of the one-year intervention and that at baseline are estimated from ANOVA and adjusted for sites.

  • cDifferences in the mean of change in percent mammographic breast density comparing study arms receiving vitamin D3 with placebo, 95% confidence intervals and P values, are estimated from ANOVA and adjusted for sites; 95% confidence intervals and P values are adjusted for multiple comparisons (Bonferroni correction).

  • dß (95% confidence interval) and P value for linear trend are estimated from regression models and adjusted for sites. 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 of vitamin D3.