Table 1.

Select characteristics of the study population

HPFS
NHS
P*
Cases (n = 168)Controls (n = 168)Cases (n = 197)Controls (n = 197)
Mean age at diagnosis or selection (y)71.070.965.565.5
Family history of colorectal cancer (%)22.616.222.616.80.04
Never smokers (%)43.545.542.147.40.64
Mean pack-years of smoking25.628.029.725.80.09
Regular aspirin use (%)19.125.234.242.60.03
Current use of postmenopausal hormone (%)32.039.6
Multivitamin use (%)54.250.945.351.60.63
Mean body mass index, kg/m226.125.826.226.40.44
Mean physical activity, MET-h/wk30.235.116.217.10.22
Red meat intake ≥1 serving/d (%)36.334.118.916.30.55
Mean dietary folate, μg/d§365.5371.7285.5296.90.35
Mean alcohol intake, g/day§10.911.26.55.90.85
Colon cancer by site
Proximal (%)44.943.3
Distal (%)31.333.9
Rectal (%)23.822.8
  • * P value for the combined NHS and HPFS cases and controls.

  • Pack-years of smoking were calculated among past and current smokers only.

  • Percentage of women using hormone replacement therapy was calculated among postmenopausal women only.

  • § Mean values calculated at baseline.