Table 2.

Linear regression analyses of NMR among Northern Plains and Southwestern smokers

Variable	B	95% CI for B	Beta	Variation in NMR accounted for by each variable a	P value
a. Both Tribal Populations Combined (n=150 included in model)
CYP2A6 Genotype b	0.18	0.11 to 0.25	0.38	14.52%	<0.001
Gender (male=1, female=0)	−0.04	−0.14 to 0.05	−0.07	0.45%	0.37
Age (years)	0.0001	−0.003 to 0.004	0.02	0.03%	0.82
Traditional Tobacco user (yes=1, no=0)	−0.01	−0.12 to 0.10	−0.02	0.03%	0.81
Body Mass Index	−0.008	−0.01 to −0.001	−0.17	1.35%	0.03
CPD	0.003	−0.004 to 0.01	0.07	0.45%	0.36
Tribal population (NP=1, SW=2)	−0.10	−0.20 to 0.002	−0.15	2.05%	0.06
b. Northern Plains Smokers (n=108 included in model)
CYP2A6 Genotype b	0.21	0.13 to 0.30	0.45	19.71%	<0.001
Body Mass Index	−0.007	−0.02 to 0.001	−0.16	2.40%	0.07
c. Southwestern Smokers (n=48 included in model)
CYP2A6 Genotype b	0.11	0.0001 to 0.22	0.29	8.12%	0.05
Body Mass Index	−0.005	−0.02 to 0.005	−0.14	1.99%	0.33

^aVariation in NMR accounted for by each variable is determined by: (Part Correlation)² x 100

^bCYP2A6 genotype was coded as 0 for individuals with no known CYP2A6 reduced activity alleles (i.e. *1A/*1A, *1A/*1B, *1B/*1B genotypes), −1 for those possessing one decrease-of-function allele (i.e. *1/*9 and *1/*12 genotypes), and −2 for those possessing one or more loss-of-function or two decrease-of-function alleles (i.e. *1/*2, *1/*4, and *9/*9 genotypes)

^cBoth tribal populations combined: R²=0.222, P<0.001. R² indicates the proportion of variance in NMR levels (22.2%) that is explained by this model.

^dNP smokers: R²=0.231, P<0.001. R² indicates the proportion of variance in NMR levels (23.1%) that is explained by this model.

^eSW smokers: R²=0.092, P=0.11. R² indicates the proportion of variance in NMR levels (9.2%) that is explained by this model