Table 2.

RRs and 95% CIs of colorectal cancer according to quartiles of HbA1c levels in the Women's Health Study

Quartile of HbA1c (%)
1234Ptrend
HbA1c, % (range)2.3-4.8>4.8-5.0>5.0-5.2≥5.2
Colorectal cancer
    No. cases36414645
    RR (95% CI)*1.001.00 (0.64-1.57)1.03 (0.66-1.60)0.89 (0.57-1.40)0.59
    RR (95% CI)1.001.02 (0.65-1.61)0.95 (0.60-1.50)0.83 (0.52-1.33)0.35
Colon cancer
    No. cases29273338
    RR (95% CI)*1.000.81 (0.48-1.36)0.89 (0.54-1.47)0.90 (0.55-1.47)0.84
    RR (95% CI)1.000.83 (0.49-1.41)0.81 (0.48-1.38)0.86 (0.51-1.44)0.65
Tumor location
    Proximal colon cancer
        No. cases15171917
        RR (95% CI)*1.000.96 (0.48-1.93)0.95 (0.48-1.89)0.74 (0.36-1.50)0.37
        RR (95% CI)1.000.89 (0.44-1.79)0.73 (0.36-1.48)0.51 (0.25-1.08)0.06
    Distal colon cancer
        No. cases14101421
        RR (95% CI)*1.000.63 (0.28-1.42)0.81 (0.39-1.72)1.09 (0.54-2.17)0.51
        RR (95% CI)1.000.74 (0.32-1.69)0.91 (0.42-2.00)1.47 (0.70-3.08)0.17
    Rectal cancer
        No. cases712126
        RR (95% CI)*1.001.64 (0.65-4.18)1.61 (0.63-4.12)0.77 (0.26-2.33)0.53
        RR (95% CI)1.001.64 (0.64-4.18)1.55 (0.60-4.01)0.60 (0.18-1.99)0.34
Tumor stage
    Duke's A
        No. cases1591711
        RR (95% CI)*1.000.55 (0.24-1.28)1.14 (0.56-2.30)0.95 (0.42-2.16)0.72
        RR (95% CI)1.000.45 (0.16-1.29)1.53 (0.59-3.99)1.23 (0.40-3.78)0.48
    Duke's B
        No. cases5131111
        RR (95% CI)*1.002.12 (0.74-6.05)2.05 (0.70-6.04)2.58 (0.86-7.78)0.14
        RR (95% CI)1.003.19 (0.83-12.26)4.98 (1.22-20.34)4.69 (1.14-19.30)0.04
    Duke's C
        No. cases15181721
        RR (95% CI)*1.001.09 (0.53-2.21)1.07 (0.52-2.18)1.54 (0.76-3.12)0.21
        RR (95% CI)1.001.35 (0.59-3.06)0.72 (0.30-1.74)1.27 (0.52-3.18)0.74
  • * Model was adjusted for age and random treatment assignment.

  • Model was adjusted for age, random treatment assignment, body mass index, family history of colorectal cancer in a first-degree relative, history of colon polyps, physical activity, smoking status, red meat intake, alcohol consumption, total energy intake, multivitamin use, menopausal status, and baseline postmenopausal hormone use.