Table 1

Comparison of case- and matched-control subjects by demographic factors, major risk factors for breast cancer, and Serum C-peptide levels, Shanghai Breast Cancer Study, 1996–1998

Cases (n = 143)Controls (n = 143)OR (95% CI)
Demographic factors
 Age (25th, 75th percentile)54 (46, 59)55 (46, 60)
 Education of high school or more (%)43.438.51.3 (0.8–2.0)
 Household income ≥15,000 (Yuan, %)69.271.30.9 (0.5–1.5)
Major risk factors
 Family history of breast cancer in mother/sister (%)3.52.11.7 (0.4–7.0)
 Ever diagnosed with breast fibroadenoma (%)7.02.83.0 (0.8–1.1)
 No regular leisure physical activity in the last 10 years (%)69.261.51.4 (0.9–2.3)
 Current WHR ≥0.80 (%)60.151.11.6 (0.9–2.7)
 Current BMI ≥23 (%)60.848.31.7 (1.0–2.7)
 Age at menarche ≤13 yr (%)24.518.91.4 (0.8–2.6)
 Age at menopause ≥50 yr (%)a48.040.21.5 (0.8–2.8)
 Age at first live birth ≥30 yr (%)b19.610.52.8 (1.1–4.5)
C-peptide levels (ng/ml)
 Mean± SD1.40 ± 1.331.11 ± 0.88P = 0.01c
 Median (25th, 75th percentile)1.06 (0.76, 1.49)0.88 (0.59, 1.20)P = 0.03d
  • a Among postmenopausal women.

  • b Among parous women.

  • c P from paired t test, using log-transformed data.

  • d P from Wilcoxon signed rank test.