Table 4.

Association between prediagnostic C-peptide concentration and prostate cancer by age at diagnosis and BMI, CLUE II, 1989-2002

Fourth of the C-peptide distribution (pmol/L)P-trend*P-interaction
Lowest (<849)Second (849-<1,367)Third (1,367-<2,017)Highest (≥2,017)
Age at diagnosis
    ≤71 y (137 pairs)
        OR1.001.060.910.700.34
        95% CIReference0.54-2.070.43-1.920.30-1.62
    >71 y (127 pairs)0.81
        OR1.000.770.460.510.09
        95% CIReference0.37-1.620.21-1.010.22-1.19
BMI
    <26.5 kg/m2 (142 cases, 132 controls)
        OR1.000.750.590.640.16
        95% CIReference0.40-1.430.30-1.170.32-1.28
    ≥26.5 kg/m2 (122 cases, 132 controls)0.29
        OR1.001.250.850.950.65
        95% CIReference0.60-2.570.40-1.810.45-2.01
  • *From a Wald test of the coefficient estimated when entering C-peptide in the model as a single ordinal variable with values corresponding to the median of the fourth into which a man's concentration fell.

  • The median was 71 y; adjusted for BMI (overweight or obese versus normal) and family history of prostate cancer (yes or missing versus no).

  • The median was 26.5 kg/m2; adjusted for BMI (continuous) and family history of prostate cancer (yes or missing versus no).