Table 1

Characteristics of Carolina Breast Cancer Study participants

Cases n = 862 n (%)Controls n = 790 n (%)OR (95% CI)a
Age at selection
≥50 years356 (41)383 (49)2.7 (2.0–3.5)b
<50 years506 (59)407 (51)1.0
Race
White527 (61)458 (58)0.8 (0.7–1.1)
Black335 (39)332 (42)1.0
Age at menarche
<12 years203 (24)164 (21)1.2 (0.9–1.6)
≥12 years658 (76)623 (79)1.0
Nulliparity/Age at first full-term pregnancy
Nulliparous133 (15)89 (11)1.1 (0.8–1.5)
>25 years187 (22)162 (21)1.0 (0.8–1.3)
≤25 years538 (63)537 (68)1.0
Abortion (spontaneous or induced)
Ever302 (35)299 (38)0.8 (0.7–1.0)
Never560 (65)491 (62)1.0
Breastfeeding
≥12 months119 (14)115 (14)0.8 (0.6–1.1)
<12 months159 (18)187 (24)0.7 (0.5–0.9)
Never583 (68)488 (62)1.0
Oral contraceptive use
Ever552 (64)470 (60)1.3 (1.0–1.7)
Never307 (36)319 (40)1.0
Hormone replacement therapy
Ever (≥3 months)207 (24)246 (31)0.8 (0.6–1.0)c
Never655 (76)544 (69)1.0
Body mass index
>27.3 kg/m2389 (45)356 (46)1.0 (0.7–1.2)
≤27.3 kg/m2467 (55)419 (54)1.0
Waist:hip ratio
>0.8448 (53)378 (48)1.4 (1.1–1.7)
≤0.8403 (47)405 (52)1.0
First-degree family history of breast or ovarian cancer
Yes140 (17)96 (13)1.5 (1.1–2.0)
No697 (83)664 (87)1.0
Medical radiation to chest area
Ever54 (06)55 (07)1.1 (0.7–1.6)
Never807 (94)735 (93)1.0
Alcohol drinking (most recent age range)
Yes507 (59)454 (57)0.9 (0.8–1.2)
No355 (41)335 (43)1.0
Smoking
Ever (≥5 packs)418 (49)367 (47)1.1 (0.9–1.3)
Never444 (51)423 (53)1.0
Education
≥College graduate243 (28)205 (26)1.2 (0.8–1.7)
≥High school graduate to <College graduate460 (53)420 (53)1.1 (0.8–1.5)
<High school graduate159 (19)165 (21)1.0
  • a Adjusted for all the 13 primary exposure variables assessed in the study, as well as race, age at diagnosis/selection (5-year age group), and the offset term.

  • b Adjusted for race, as well as all the 13 primary exposure variables assessed in the study and the offset term.

  • c Additionally adjusted for menopausal status.