Table 1.

Distribution of demographic characteristics and known breast cancer risk factors for cases and controls included in the study

CategoryCases (N = 3,472)Controls (N = 3,595)P
Demographic factorsa
 Age, y (±SD)53.2 ± 10.053.0 ± 9.30.38
 Education ≥ high school (%)55.940<0.01
Reproductive risk factors
 Age at menarche (y)14.4 ± 1.714.9 ± 1.8<0.01
 Postmenopausal (%)b49.853.1<0.01
 Age at menopauseb49.0 ± 4.248.8 ± 3.90.29
 Age at first live birth (y)c26.9 ± 3.825.6 ± 4.1<0.01
Other risk factors
 First-degree relative with breast cancer (%)5.32.2<0.01
 Body mass index24.1 ± 3.523.9 ± 3.40.05
 Body mass indexb24.7 ± 3.724.4 ± 3.50.01
  • aUnless otherwise specified, mean ± SD are presented.

  • bAmong postmenopausal women.

  • cAmong parous women.