Table 1 Comparison of characteristics of women participating in the California Teachers Study mammographic density substudy who were included in the analyses with those of participants who were excluded from the analyses

At cohort enrollment

Age (mean ± SD)

49.9 ± 4.2 (range 40-60)

50.5 ± 3.8 (range 41-60)

BMI (kg/m²)

24.6 ± 4.8 (range 17-50)

24.7 ± 4.9 (range 17-47)

White (N (%))

624 (87%)

284 (100%)

Nulliparous women (N (%))

141 (20%)

63 (22%)

Menopausal status

 Premenopausal

432 (60%)

155 (55%)

 Perimenopausal

87 (12%)

55 (19%)

 Postmenopausal

201 (28%)

74 (26%)

Ever had breast biopsy (N (%))

108 (15%)

40 (14%)

Positive 1st degree family history of breast cancer (N (%))

64 (9%)

37 (13%)

At mammogram substudy enrollment

Age at interview (mean ± SD)

62 ± 4.0 (range 52-71)

62 ± 3.6 (range 53-72)

BMI (kg/m²)

26.2 ± 5.2 (range 17-49)

25.7 ± 5.0 (range 18-47)

Positive 1st degree family history of breast cancer (N (%))

112 (16%)

51 (18%)

Number of mammograms in the past 10 years

8.8 ± 2.3 (range 2-20)

8.9 ± 2.2 (range 2-18)

At time of mammography evaluated for density

Age at time of mammogram while taking EPT

56 ± 4 (range 45-67)

Age at time of mammogram while off EPT

60 ± 5 (range 49-71)

BMI at time of mammogram while taking EPT

25.7 ± 5.2 (range 18-47)

BMI at time of mammogram while off EPT

25.8 ± 5.0 (range 18-48)

Years on EPT at time of mammogram while taking EPT

 <1 year

15 (5%)

 1- < 4 years

121 (43%)

 4- < 7 years

112 (39%)

 ≥7 years

36 (13%)

Time interval between two mammograms (years)

 ≤3 years

141 (50%)

 4-5 years

106 (37%)

 6-9 years

37 (13%)