Table 1

Comparison of cases and controls by selected descriptive characteristics, Shanghai Breast Cancer Study, 1996–1998

Subject characteristicsCases (n = 1144)Controls (n = 1236)Pa
Age, yr (mean ± SD)46.4 ± 9.946.7 ± 8.80.42
Education, %
 No formal education3.86.0
 Elementary school8.58.6
 Middle or high school75.875.3
 College or above12.010.1<0.05
Breast cancer in first-degree relative, %3.42.40.15
Ever had breast fibroadenoma, %9.75.2<0.01
Age at menarche (yr)14.5 ± 1.614.7 ± 1.7<0.01
Ever had a live birth, %94.995.90.27
 Number of live births, mean ± SD1.5 ± 0.81.5 ± 0.90.19
 Age at first live birth, yr (mean ± SD)26.8 ± 4.126.2 ± 3.8<0.01
Postmenopausal, %33.336.30.13
Age at menopause, yr (mean ± SD)48.2 ± 4.647.4 ± 5.00.03
Physically active past 10 yr, %19.325.8<0.01
Body mass index, kg/m2 (mean ± SD)23.6 ± 3.423.2 ± 3.40.02
Waist-to-hip ratio, mean ± SD0.81 ± 0.060.80 ± 0.06<0.01
Daily animal food intake, g (mean ± SD)90.4 ± 61.879.4 ± 50.1<0.01
Daily plant food intake, g (mean ± SD)501 ± 275496 ± 2780.73
Daily folate intake, μg (mean ± SD)287 ± 141303 ± 1790.02
Daily methionine intake, g (mean ± SD)1.72 ± 0.601.65 ± 0.56<0.01
Daily vitamin B12 intake, μg (mean ± SD)4.77 ± 4.114.69 ± 4.200.66
Daily vitamin B6 intake, mg (mean ± SD)1.83 ± 0.601.77 ± 0.570.03
Daily energy intake, kcal (mean ± SD)1875 ± 4671852 ± 4590.23
  • a For χ2 test (categorical variables) or t test (continuous variables).