Table 3.

RR and 95% CI of colorectal cancer according to quartiles of plasma levels of C-peptide, IGFBP-1, and HbA1c in the Nurses' Health Study, 1989-2000

Quartile
Ptrend
1234
C-peptide
    Median (ng/mL)0.91.42.03.6
Colorectum
        Cases/Controls35/8750/8654/8943/88
        RR* (95% CI)1.001.46 (0.86-2.45)1.50 (0.88-2.57)1.22 (0.70-2.13)
        RR (95% CI)1.001.46 (0.84-2.53)1.41 (0.79-2.55)1.17 (0.63-2.20)0.94
Colon
        Cases/Controls23/7041/6542/7134/62
        RR* (95% CI)1.001.88 (1.04-3.42)1.83 (0.96-3.48)1.65 (0.88-3.09)
        RR (95% CI)1.001.88 (1.00-3.56)1.85 (0.92-3.74)1.76 (0.85-3.63)0.38
IGFBP-1
    Median (ng/mL)5.719.131.855.7
Colorectum
        Cases/Controls34/4325/6141/6228/70
        RR* (95% CI)1.000.42 (0.21-0.83)0.81 (0.45-1.44)0.45 (0.23-0.89)
        RR (95% CI)1.000.41 (0.19-0.86)0.82 (0.42-1.62)0.48 (0.21-1.09)0.31
Colon
        Cases/Controls30/3320/5228/5321/51
        RR* (95% CI)1.000.39 (0.18-0.82)0.61 (0.31-1.17)0.42 (0.20-0.89)
        RR (95% CI)1.000.32 (0.14-0.75)0.45 (0.20-1.01)0.28 (0.11-0.75)0.05
HbA1c§
    Median (%)5.15.45.65.8
Colorectum
        Cases/Controls41/7340/8948/8746/83
        RR*1.000.82 (0.48-1.41)1.01 (0.59-1.73)0.99 (0.57-1.71)
        RR1.000.75 (0.43-1.30)0.94 (0.54-1.65)0.85 (0.47-1.51)0.74
Colon
        Cases/Controls33/5526/7041/6635/64
        RR*1.000.66 (0.35-1.23)1.08 (0.59-1.98)0.95 (0.51-1.76)
        RR1.000.57 (0.29-1.10)1.02 (0.53-1.95)0.82 (0.42-1.61)0.91
  • * RR from conditional logistic regression.

  • RR from conditional logistic regression additionally adjusted for BMI, physical activity, pack-years smoked, and alcohol intake as continuous variables, family history of colorectal cancer, aspirin use, history of screening, menopausal status, and use of postmenopausal hormones.

  • IGFBP-1 reported only among women who reported their blood collection was 6 or more hours since their last meal (128 cases/236 controls).

  • § The total number of cases and controls for HbA1c is less than that for C-peptide due to missing data.