Table 1.

Comparison of individuals in the Aspirin/Folate Polyp Prevention Trial who participated and did not participate in this study

CharacteristicsIndividuals excluded in this studyIndividuals included in this studyP*
No. participants733388
Age at baseline, mean ± SD (y)57.3 ± 9.957.8 ± 9.10.83
Male, n (%)466 (63.6)246 (63.4)0.96*
Body mass index >30 kg/m2, n (%)176 (24.0)77 (19.9)0.12*
Current cigarette smoker, n (%)106 (14.5)58 (15.0)0.97*
Colorectal cancer in first-degree relative, n (%)224 (36.9)117 (37.9)0.78*
Self-identified as White, n (%)633 (86.4)325 (83.8)0.24*
Aspirin Treatment Group, n (%)489 (66.7)260 (67.0)0.92*
Folate Treatment Group, n (%)318 (50.2)198 (51.0)0.81*
Baseline RBC folate, mean ± SD (ng/mL)414.9 ± 6.3396.4 ± 7.20.04§
Baseline plasma folate, mean ± SD (nmol/L)24.8 ± 0.7520.9 ± 0.80<0.01§
Baseline plasma B2, mean ± SD (nmol/L)30.9 ± 2.125.7 ± 2.30.38§
Baseline plasma B6, mean ± SD (nmol/L)80.7 ± 3.576.5 ± 4.60.44§
Baseline plasma B12, mean ± SD (pmol/L)319.3 ± 6.2338.6 ± 9.10.09§
Baseline plasma homocysteine, mean ± SD (μmol/L)10.1 ± 4.29.9 ± 2.950.80§
Multivitamin use, n (%)265 (36.3)130 (33.5)0.36§
Dietary intake
    Folate intake, mean ± SD (μg/d)327.9 ± 6.1305.0 ± 7.70.01
    Vitamin B2, mean ± SD (mg/d)1.79 ± 0.031.72 ± 0.430.11
    Vitamin B6, mean ± SD (mg/d)1.67 ± 0.031.64 ± 0.040.26
    Vitamin B12, mean ± SD (mg/d)
Alcohol (drinks/d), n (%)217 (31.5)123 (33.0)0.21*
    None341 (49.4)165 (44.2)
    ≤1132 (19.1)85 (22.8)
    ≥2
Adenoma characteristics (at baseline)
    No. lifetime adenomas (mean ± SD)2.44 ± 2.302.22 ± 1.940.11§
    Large baseline adenomas (>1 cm), n (%)157 (21.4)96 (24.7)0.21*
    Baseline adenomas with villous histology, n (%)107 (14.6)49 (12.6)0.37*
    Baseline adenomas with proximal location, n (%)342 (46.7)164 (42.3)0.16*
  • * χ2 test.

  • Two-sample t test.

  • 81 and 325 mg/d aspirin treatment groups combined.

  • § Nonparametric Mann-Whitney test.

  • Using standard definitions by Polyp Prevention Study Group (30, 31).