Table 2.

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

	Base model			Including covariates from stepwise regression
Independent variables	Cumulative R²	Regression coefficient	P	Cumulative R²	Regression coefficient	P
MHBMA, ng/mg Cr
Age, y		0.00004	1.00		0.005	0.16
Japanese American vs. whites		−0.429	<0.0001		−0.106	0.22
Native Hawaiian vs. whites		−0.238	0.02		−0.212	0.01
Nicotine equivalents, nmol/mL		0.188	0.002		0.187	0.0002
BMI, kg/m²		−0.050	0.81		0.128	0.45
Sex	5.30%	0.038	0.65		0.116	0.10
+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, y		0.005	0.08		0.007	0.02
Japanese American vs. whites		−0.087	0.19		−0.020	0.77
Native Hawaiian vs. whites		−0.124	0.07		−0.072	0.29
Nicotine equivalents, nmol/mL		0.001	0.97		0.238	0.54
BMI, kg/m²		−0.057	0.67		0.025	0.85
Sex	2.50%	0.121	0.03		0.181	0.001
+Alcohol (g/1,000 kcal/d)^a				5.80%	0.010	<0.0001
MHBMA/(MHBMA + DHBMA)
Age, y		−0.005	0.29		−0.002	0.68
Japanese American vs. whites		−0.338	0.001		−0.097	0.29
Native Hawaiian vs. whites		−0.117	0.27		−0.154	0.09
Nicotine equivalents, nmol/mL		0.186	0.003		0.151	0.004
BMI, kg/m²		0.012	0.96		0.076	0.67
Sex	4.90%	−0.078	0.36		−0.088	0.24
+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)^a				32.6%	−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.