Table 2.

Selected characteristics of the study population

Population-based familiesClinic-based families
Cases (n = 1,806)Sibling controls (n = 2,879)P*Cases (n = 269)Sibling controls (n = 475)P
Person characteristic
    Mean age ± SD53.5 ± 10.954.0 ± 11.8<0.0149.1 ± 11.451.4 ± 11.8<0.01
    Sex, no. (%)
        Male927 (51.3)1278 (44.4)<0.01133 (49.4)204 (42.9)0.19
        Female879 (48.7)1601 (55.6)136 (50.6)271 (57.1)
    Race, no. (%)
        Non-Hispanic white1580 (87.5)2512 (87.3)1.00262 (97.4)463 (97.5)1.00
        Black32 (1.8)42 (1.5)1 (0.4)2 (0.4)
        Asian69 (3.8)113 (3.9)0 (0)0 (0)
        Other104 (5.8)189 (6.6)5 (1.9)9 (1.9)
        Unknown/missing21 (1.2)23 (0.8)1 (0.4)1 (0.2)
    Center, no. (%)
        Ontario, Canada308 (17.1)515 (17.9)0 (0)0 (0)1.00
        USC Consortium, U.S.384 (21.3)519 (18.0)38 (14.1)48 (10.1)
        Melbourne, Australia344 (19.0)611 (21.2)110 (40.9)213 (44.8)
        Hawaii, U.S.63 (3.5)103 (3.6)0 (0)0 (0)
        Mayo Foundation, U.S.282 (15.6)526 (18.3)121 (45.0)214 (45.1)
        Seattle, U.S.425 (23.5)605 (21.0)0 (0)0 (0)
Family history of colorectal cancer, no. (%)
No first -degree relative1177 (65.2)101 (37.5)
At least first-degree relative546 (30.2)70 (26.0)
Unknown/Missing83 (4.6)98 (36.4)
    BMI (kg/m2)
        15-18 (underweight)22 (1.2)25 (0.9)<0.016 (2.2)12 (2.5)0.82
        18-25 (normal)629 (34.8)1155 (40.1)97 (36.1)174 (36.6)
        25-30 (overweight)670 (37.1)1036 (36.0)100 (37.2)174 (36.6)
        30+ (obese)422 (23.4)594 (20.6)53 (19.7)92 (19.4)
        Unknown/missing63 (3.5)69 (2.4)13 (4.8)23 (4.8)
    Alcohol use (drinks/wk)
        None467 (25.9)829 (28.8)0.0876 (28.3)132 (27.8)0.43
        1-7 (moderate)857 (47.5)1353 (47.0)124 (46.1)226 (47.2)
        8+ (heavy)229 (12.7)362 (12.6)39 (14.5)61 (12.8)
        Unknown/missing253 (14.0)335 (11.6)30 (11.2)56 (11.8)
    Smoking
        Never781 (43.2)1309 (45.5)0.24138 (51.3)226 (47.6)<0.01
        Former632 (35.0)1001 (34.8)58 (21.6)153 (32.2)
        Current343 (19.0)509 (17.7)66 (24.5)87 (18.3)
        Unknown/missing50 (2.8)60 (2.1)7 (2.6)9 (1.9)
    Folate supplements§
        No1586 (87.8)2557 (88.8)0.14233 (86.6)411 (91.3)0.25
        Yes196 (10.9)274 (9.5)31 (11.5)39 (8.7)
        Unknown/missing24 (1.3)48 (1.7)5 (1.9)11 (2.3)
Multivitamins§
        No820 (45.4)1497 (52.0)<0.01138 (51.3)267 (56.2)0.27
        Yes971 (53.8)1346 (46.8)129 (48.0)200 (42.1)
    Calcium supplements§
        No1335 (73.9)2063 (71.7)0.03208 (77.3)345 (76.7)0.33
        Yes459 (25.4)785 (27.3)56 (20.8)105 (23.3)
Unknown/missing12 (0.7)31 (1.1)5 (1.9)2 (0.4)
    Dietary folate (μg; mean ± SD)327.4 ± 118.7334.1 ± 126.80.32349.6 ± 154.9346.0 ± 145.00.95
    Total folate DFE (mean ± SD)477 ± 265.6525.4 ± 439.7<0.01606.5 ± 463.1549.6 ± 322.20.29
    Dietary B12 (mean ± SD)3.0 ± 1.22.9 ± 1.30.673.1 ± 1.43.0 ± 1.40.36
    Total B12 (mean ± SD)6.2 ± 6.47.4 ± 11.8<0.0110.0 ± 17.68.8 ± 10.00.41
    Dietary B6 (mean ± SD)1.1 ± 0.41.1 ± 0.40.261.1 ± 0.51.1 ± 0.40.64
    Total B6 (mean ± SD)1.9 ± 2.02.3 ± 3.8<0.013.0 ± 6.02.6 ± 3.30.48
Tumor characteristics
    Site, no. (%)
        Right colon598 (33.1)85 (31.6)
        Left colon525 (29.1)44 (16.4)
        Rectum593 (32.8)77 (28.6)
        Unknown/missing90 (5.0)63 (23.4)
    MSI, no. (%)
        MSS855 (47.3)61 (22.7)
        MSI-L151 (8.4)14 (5.2)
        MSI-H179 (9.9)55 (20.4)
        Unknown/missing621 (34.4)139 (51.7)

Abbreviations: DFE, dietary folate equivalent; BMI, body mass index.

  • *P values using a 1-df likelihood test from a conditional logistic regression model.

  • Includes individuals who self-identified themselves as Hispanic, Native, Hawaiian/Pacific Islander, and mixed race.

  • Self-reported weight and height (2 y before the questionnaire completion date) used to calculate body mass index.

  • §Ever use of supplements regularly during the 2 y before recruitment (at least twice per week for more than a month).

  • Calorie-adjusted calculated from the food frequency questionnaire using postfortification food composition tables (n cases = 585; n controls = 837).