Table 3.

Meana mammographic percent density prior to CaD randomization (CaD baseline), approximately one year after CaD randomization (CaD follow-up), and ratio of means by CaD randomization assignment by subgroup

Mean% mammographic density (SD)
nAt CaD baselineAt CaD follow-UpRatio of CaD baseline to follow-up (95% CI)Ratio in CaD vs. ratio in placebo (95% CI)P (int)b
Age0.31
 50–57 y
  CaD594.6 (3.0–6.9)4.2 (2.9–6.1)0.92 (0.74–1.15)0.95 (0.71–1.27)
  Placebo533.1 (2.0–4.8)3.0 (2.0–4.6)0.97 (0.81–1.17)
 58–65 y
  CaD643.2 (2.1–4.7)3.2 (2.1–4.9)1.02 (0.81–1.27)0.77 (0.56–1.07)
  Placebo441.9 (1.1–3.5)2.5 (1.5–4.2)1.32 (1.04–1.66)
 66–79 y
  CaD563.6 (2.2–5.9)3.6 (2.3–5.5)1.00 (0.77–1.30)1.20 (0.83–1.72)
  Placebo543.6 (2.3–5.6)3.0 (1.8–4.8)0.83 (0.65–1.08)
Total vitamin D intake (IU/d)0.75
 <200
  CaD873.6 (2.5–5.2)3.5 (2.5–4.9)0.96 (0.79–1.18)0.97 (0.74–1.28)
  Placebo773.0 (2.1–4.5)3.0 (2.1–4.3)0.99 (0.83–1.19)
 200 to <400
  CaD292.4 (1.1–5.3))2.8 (1.4–5.6)1.13 (0.73–1.74)0.89 (0.53–1.47)
  Placebo242.5 (1.3–5.1)3.2 (1.7–6.1)1.28 (1.03–1.59)
 ≥400
  CaD534.3 (2.9–6.4)4.0 (2.6–6.0)0.93 (0.77–1.14)1.06 (0.75–1.50)
  Placebo442.7 (1.5–4.8)2.3 (1.3–4.2)0.88 (0.65–1.19)
Total calcium Intake (mg/d)0.51
 <750
  CaD773.6 (2.4–5.2)3.2 (2.2–4.6)0.90 (0.71–1.14)0.99 (0.74–1.34)
  Placebo713.1 (2.1–4.6)2.8 (1.9–4.2)0.91 (0.75–1.09)
 750 to <1,000
  CaD403.7 (1.9–7.2)4.4 (2.6–7.5)1.19 (0.88–1.62)1.16 (0.75–1.80)
  Placebo322.7 (1.4–5.1)2.7 (1.6–4.7)1.03 (0.74–1.43)
 ≥1,000
  CaD523.5 (2.3–5.1)3.3 (2.2–5.1)0.96 (0.78–1.16)0.83 (0.61–1.15)
  Placebo422.5 (1.4–4.7)2.9 (1.7–5.1)1.14 (0.88–1.49)
Active HT0.08
 No
  CaD872.7 (1.9–3.8)2.3 (1.6–3.3)0.86 (0.70–1.07)0.82 (0.61–1.11)
  Placebo861.9 (1.3–2.8)2.0 (1.4–2.9)1.05 (0.85–1.29)
 Yes
  CaD925.1 (3.6–7.1)5.6 (4.3–7.3)1.10 (0.93–1.30)1.16 (0.92–1.45)
  Placebo654.7 (3.2–6.9)4.5 (3.0–6.6)0.95 (0.83–1.09)
Gail risk score0.23
 <1.25
  CaD1093.3 (2.4–4.5)3.1 (2.3–4.2)0.95 (0.80–1.14)0.90 (0.70–1.15)
  Placebo893.0 (2.1–4.2)3.1 (2.3–4.3)1.06 (0.90–1.25)
 1.25 to <1.75
  CaD424.2 (2.3–7.6)4.2 (2.5–7.1)1.02 (0.75–1.37)1.01 (0.65–1.57)
  Placebo351.9 (0.9–3.7)1.9 (1.0–3.6)1.00 (0.72–1.39)
 ≥1.75
  CaD285.2 (3.2–8.5)5.4 (3.3–8.7)1.03 (0.81–1.30)1.22 (0.84–1.78)
  Placebo274.2 (2.5–7.3)3.6 (1.8–7.0)0.84 (0.62–1.14)
Race/ethnicity0.11
 White
  CaD822.9 (1.9–4.3)3.3 (2.4–4.7)1.17 (0.95–1.42)1.18 (0.90–1.55)
  Placebo782.9 (1.9–4.3)2.8 (1.9–4.1)0.99 (0.82–1.19)
 Black
  CaD654.4 (3.0–6.6)3.6 (2.4–5.4)0.81 (0.63–1.03)0.76 (0.55–1.06)
  Placebo542.6 (1.6–4.1)2.7 (1.8–4.3)1.06 (0.86–1.30)
 Hispanic
  CaD254.3 (2.6–7.2)4.1 (2.5–6.6)0.95 (0.74–1.23)0.85 (0.52–1.40)
  Placebo142.3 (0.8–6.4)2.6 (1.1–5.9)1.12 (0.66–1.89)
BMI (kg/m2)0.31
 Normal (<25)
  CaD356.8 (4.3–10.7)5.5 (3.3–9.3)0.81 (0.66–1.01)0.79 (0.58–1.06)
  Placebo377.5 (4.9–11.5)7.7 (5.0–12.0)1.04 (0.83–1.29)
 Overweight (25 to <30)
  CaD633.8 (2.5–5.8)3.5 (2.3–5.5)0.94 (0.73–1.20)1.02 (0.71–1.46)
  Placebo504.2 (2.8–6.4)3.9 (2.5–6.0)0.92 (0.71–1.20)
 Obese (≥30)
  CaD812.8 (1.9–4.2)3.1 (2.3–4.2)1.09 (0.89–1.34)1.03 (0.77–1.38)
  Placebo631.2 (0.8–1.8)1.2 (0.8–1.8)1.06 (0.86–1.30)
Solar irradiation (Langleys)0.13
 <350
  CaD342.4 (1.1–5.0)3.2 (1.8–5.9)1.36 (0.92–2.00)1.53 (1.00–2.32)
  Placebo482.7 (1.6–4.5)2.4 (1.4–4.1)0.89 (0.71–1.12)
 350 to <400
  CaD943.9 (2.8–5.5)3.5 (2.5–4.8)0.88 (0.73–1.06)0.78 (0.58–1.04)
  Placebo622.5 (1.6–3.9)2.8 (1.9–4.1)1.13 (0.91–1.40)
 ≥400
  CaD514.5 (3.1–6.6)4.3 (3.0–6.2)0.96 (0.80–1.14)0.98 (0.74–1.31)
  Placebo413.7 (2.2–6.2)3.6 (2.2–5.9)0.97 (0.76–1.24)
Category of mammographic density0.42
 <1%
  CaD350.3 (0.2–0.4)0.5 (0.3–0.7)1.78 (1.14–2.78)1.23 (0.70–2.18)
  Placebo390.3 (0.2–0.4)0.4 (0.3–0.6)1.45 (0.99–2.10)
 1%–<10%
  CaD873.6 (3.2–4.2)3.2 (2.5–4.0)0.87 (0.73–1.04)0.97 (0.76–1.24)
  Placebo713.3 (2.8–3.9)3.0 (2.4–3.8)0.90 (0.76–1.01)
 ≥10%
  CaD5719.2 (17.3–21.5)15.5 (13.1–18.4)0.81 (0.70–0.92)0.93 (0.77–1.13)
  Placebo4119.3 (16.7–22.4)16.7 (13.7–20.4)0.86 (0.76–0.98)

NOTE: HT = hormone therapy.

  • aGeometric mean.

  • bP for interaction.