Table 1

Distribution of breast cancer cases and controls and AORa estimates for several established breast cancer risk factors and subject characteristics

VariableCases (n = 3133)Controls (n = 3062)AOR
No.b(%)No.b(%)
Breast cancer in first-degree relativec
 No2433(82)2527(89)1.0
 Yes521(18)308(11)1.72 (1.48, 2.00)
Benign breast cysts
 No1312(45)2185(75)1.0
 Yes1621(55)720(25)3.71 (3.32, 4.15)
Age at menarche
 ≤11588(19)540(18)1.0
 12788(26)733(24)0.99 (0.85, 1.16)
 13907(29)880(29)0.94 (0.81, 1.09)
 ≥14806(26)868(29)0.83 (0.71, 0.97)
Parityd
 Nulliparous461(15)377(12)1.0
 1398(13)357(12)0.94 (0.77, 1.16)
 2–31725(56)1673(55)0.85 (0.72, 1.01)
 ≥4520(17)629(21)0.64 (0.52, 0.77)
Age at menopausee
 <45612(21)647(23)1.0
 45–49550(19)531(19)1.09 (0.93, 1.28)
 ≥50903(31)736(26)1.27 (1.09, 1.48)
 Premenopausal859(29)949(33)
HRT usef
 No1235(40)1128(37)1.0
 Yes996(32)946(31)0.96 (0.85, 1.09)
 Premenopausal859(28)949(31)N/Aa
Age group
 25–39210(7)264(9)N/A
 40–44275(9)288(9)N/A
 45–49420(13)393(13)N/A
 50–54469(15)517(17)N/A
 55–59461(15)318(14)N/A
 60–64453(15)388(13)N/A
 65–69469(15)440(14)N/A
 70–74376(12)354(12)N/A
Highest level of education
 Elementary399(13)426(14)1.0
 High school1469(47)1386(46)1.18 (1.01, 1.38)
 Postsecondary1246(40)1221(40)1.19 (1.00, 1.40)
Marital status
 Currently married2319(74)2293(75)1.0
 Widow/separated/divorced797(26)747(25)1.04 (0.92, 1.17)
  • a AOR, age-adjusted OR; N/A, nonapplicable.

  • b Numbers may not add to total because of missing values.

  • c Mother, sister, or daughter.

  • d Live births.

  • e Last menstrual period.

  • f Hormone replacement therapy for at least 2 months.