Table 2.

Adjusted RRs of colon and rectal cancers in relation to quintiles of GI and GL, Iowa Women's Health Study (1986-2000)

FactorQuintile
P for trend
12345
Colon cancer (n events = 757)
    GI by BMI
        BMI (<25 kg/m2)
            n events5436405664
            RR, multiply-adjusted*1.00.630.701.031.030.23
            95% CI0.41-0.990.46-1.080.70-1.520.70-1.51
        BMI (25-30 kg/m2)
            n events5847685959
            RR, multiply-adjusted*1.00.711.070.920.930.82
            95% CI0.48-1.060.75-1.540.63-1.330.64-1.34
        BMI (≥30 kg/m2)
            n events3939423759
            RR, multiply-adjusted1.01.061.070.921.450.21
            95% CI0.68-1.660.69-1.670.58-1.450.96-2.19
        BMI (≥30 kg/m2), nondiabetics
            n events3231373252
            RR, multiply-adjusted1.01.011.121.001.600.07
            95% CI0.62-1.660.69-1.800.61-1.641.02-2.51
    GL by BMI
        BMI (<25 kg/m2)
            n events4453496044
            RR, multiply-adjusted1.01.090.981.140.740.26
            95% CI0.71-1.650.64-1.500.76-1.720.47-1.14
BMI (25-30 kg/m2)
            n events5866584663
            RR, multiply-adjusted1.00.960.850.721.100.81
            95% CI0.66-1.390.58-1.250.48-1.080.76-1.58
BMI (≥30 kg/m2)
            n events3239505243
            RR, multiply-adjusted1.01.141.541.721.68<0.01
            95% CI0.71-1.830.97-2.441.09-2.701.06-2.67
BMI (≥30 kg/m2), nondiabetics
            n events2134424938
            RR, multiply-adjusted1.01.502.022.392.12<0.01
            95% CI0.87-2.601.18-3.451.42-4.031.24-3.64
Rectal cancer (n events = 209)
    GI by BMI
        BMI (<25 kg/m2)
            n events161620159
            RR, multiply-adjusted1.01.021.131.000.520.16
            95% CI0.50-2.090.56-2.280.48-2.060.22-1.23
        BMI (25-30 kg/m2)
            n events161819159
            RR, multiply-adjusted1.01.081.110.750.580.12
            95% CI0.53-2.160.55-2.240.35-1.620.25-1.33
        BMI (≥30 kg/m2)
            n events410101715
            RR, multiply-adjusted1.02.382.433.843.340.02
            95% CI0.73-7.770.76-7.791.27-11.621.09-10.20
        BMI (≥30 kg/m2), nondiabetics
            n events3971513
            RR, multiply-adjusted1.02.772.265.074.220.01
            95% CI0.73-10.50.58-8.781.46-17.61.19-14.9
    GL by BMI
        BMI (<25 kg/m2)
            n events1617121516
            RR, multiply-adjusted1.01.140.730.870.880.54
            95% CI0.55-2.350.32-1.630.41-1.880.41-1.86
        BMI (25-30 kg/m2)
            n events1815151811
            RR, multiply-adjusted1.00.710.710.950.660.54
            95% CI0.34-1.500.33-1.500.47-1.920.30-1.44
        BMI (≥30 kg/m2)
            n events810121313
            RR, multiply-adjusted1.01.261.171.992.230.04
            95% CI0.49-3.240.43-3.170.81-4.890.91-5.45
        BMI (≥30 kg/m2), nondiabetics
            n events68101112
            RR, multiply-adjusted1.01.331.712.202.620.03
            95% CI0.46-3.880.60-4.890.80-6.060.97-7.09
  • * Adjusted for age (continuous), energy (quintiles), activity level (high, medium, low), multivitamin use (yes, no), diabetes (yes, no), smoking (pack-years), BMI (quintiles), and waist/hip ratio (quintiles).

  • Adjusted for all characteristics listed above, except adjusted for BMI (continuous) within BMI quintiles.