Table 1.

Baseline characteristics of the study sample by colorectal adenoma cases and controls in the PLCO Cancer Screening Triala

Serologic sampleGenotyped sample
CharacteristicCases (n = 356)Controls (n = 396)PbCases (n = 770)Controls (n = 777)Pb
Sex, % male65.265.4Matched69.269.00.92
Race, % Caucasian89.690.4Matched93.993.80.99
Age, y62.0 (58.0–66.0)62.0 (58.5–66.0)Matched62.0 (58.0–67.0)60.0 (57.0–65.0)<0.0001
BMI, kg/m227.1 (24.3–30.1)26.6 (24.3–29.2)0.3627.5 (24.7–30.5)27.0 (24.6–30.1)0.11
Smoking status, %
 Never42.747.50.1833.940.5<0.0001
 Former43.839.747.147.1
 Current8.76.114.36.8
 Pipe/cigar4.86.84.75.5
Physically active23.627.80.3519.124.20.005
 ≥5 h/wk, %
Education, %
 High school or less28.929.80.9234.029.20.001
 Some college31.732.335.831.8
 College graduate/postgraduate39.337.930.139.0
Regularc NSAID use, %53.760.60.0658.460.50.44
Aspirin dose ≥1/d, %23.626.50.3825.726.60.90
Family history of colorectal cancer, %12.17.80.0713.09.30.02
Diabetes, %6.26.80.728.17.00.44
Current use of menopausal hormone therapy, %13.814.90.8714.916.70.52
Dietary intaked
 Total energy, kcal/d2,101 (1,560–2,608)2,031 (1,593–2,701)0.941,976 (1,464–2,592)2,031 (1,564–2,643)0.15
 Saturated fat, g/1,000 kcal10.8 (9.0–12.4)10.6 (8.8–12.5)0.9211.4 (9.4–13.1)11.2 (9.4–13.1)0.86
 Fiber, g/1,000 kcal11.1 (9.1–13.4)11.5 (9.4–13.8)0.2610.5 (8.4–12.9)10.9 (8.9–13.5)0.008
 Red meat, g/1,000 kcal34.5 (21.5–50.4)31.3 (20.1–46.9)0.0836.7 (23.6–53.1)35.9 (21.6–51.4)0.27
 Dietary iron, mg/1,000 kcal8.6 (7.5–9.9)8.7 (7.4–10.3)0.658.2 (7.1–9.8)8.5 (7.3–9.9)0.05
 Supplemental iron, mg/d0 (0–18)0 (0–18)0.200 (0–18)0 (0–18)0.21
 Heme iron, μg/1,000 kcal185 (118–286)170 (108–261)0.14204 (128–305)202 (114–297)0.27
 Dietary calcium, mg/1,000 kcal419 (332–533)426 (341–540)0.90416 (349–533)429 (357–540)0.19
 Dietary folate, μg/1,000 kcal174 (142–215)177 (143–216)0.84166 (134–207)173 (142–211)0.01
 Alcohol, g/d2.7 (0.4–18.2)1.9 (0.3–10.5)0.032.8 (0.1–17.2)2.4 (0.1–15.8)0.33
Serum markers at baseline, median (IQR)
 CRP, mg/L1.64 (0.82–3.54)1.78 (0.82–4.09)0.29
 Ferritin, ng/mL140 (92–240)161 (84–277)0.53
 Iron, μg/dL107 (86–132)106 (86–131)0.93
 Transferrin saturation, %31 (25–39)30 (25–37)0.25
 TIBC, μg/dL347 (311–386)351 (324–390)0.07
 UIBC, μg/dL238 (195–279)243 (210–280)0.05
  • aAll values are median (IQR) unless otherwise specified.

  • bP values derived from the Wilcoxon rank-sum test for continuous data and from the χ2 test for categorical data.

  • cRegular use defined as ≥1/wk.

  • dDietary data: For serologic sample, n = 342 cases and 384 controls, with a further 3 cases and 1 control missing data for total dietary iron and heme iron. For genotyped sample, n = 729 cases and 754 controls.