Table 2.

Demographic, smoking, and nutritional determinants of 1,3-butadiene metabolites

Base modelIncluding covariates from stepwise regression
Independent variablesCumulative R2Regression coefficientPCumulative R2Regression coefficientP
MHBMA, ng/mg Cr
 Age, y0.000041.000.0050.16
 Japanese American vs. whites−0.429<0.0001−0.1060.22
 Native Hawaiian vs. whites−0.2380.02−0.2120.01
 Nicotine equivalents, nmol/mL0.1880.0020.1870.0002
 BMI, kg/m2−0.0500.810.1280.45
 Sex5.30%0.0380.650.1160.10
+GSTT1 (1/0) vs.(1/1)a−0.495<0.0001
(0/0) vs. (1/1)37.1%−1.563<0.0001
DHBMA, ng/mg Cr
 Age, y0.0050.080.0070.02
 Japanese American vs. whites−0.0870.19−0.0200.77
 Native Hawaiian vs. whites−0.1240.07−0.0720.29
 Nicotine equivalents, nmol/mL0.0010.970.2380.54
 BMI, kg/m2−0.0570.670.0250.85
 Sex2.50%0.1210.030.1810.001
+Alcohol (g/1,000 kcal/d)a5.80%0.010<0.0001
MHBMA/(MHBMA + DHBMA)
 Age, y−0.0050.29−0.0020.68
 Japanese American vs. whites−0.3380.001−0.0970.29
 Native Hawaiian vs. whites−0.1170.27−0.1540.09
 Nicotine equivalents, nmol/mL0.1860.0030.1510.004
 BMI, kg/m20.0120.960.0760.67
 Sex4.90%−0.0780.36−0.0880.24
+GSTT1 (1/0) vs. (1/1)a−0.458<0.0001
(0/0) vs. (1/1)30.5%−1.427<0.0001
+Alcohol (g/1,000 kcal/d)a32.6%−0.005<0.0001

NOTE: Variables allowed to compete in the stepwise regression: GSTT1 copy number polymorphism, CYP2A6 activity, smoking duration (years), and intakes of cruciferous vegetable, total fruits, caffeine, green leafy vegetables, total vegetables, alcohol, processed meats, and soy.

  • aAdditional predictor identified through stepwise regression.