Table II.

Cigarettes per day by CYP2A6 genotype group

Cigarettes per daya	SCCS, n = 483		MDA, n = 405		Pooled studies, n = 888
	Mean (95% CI)	P	Mean (95% CI)	P	Mean (95% CI)	P
CYP2A6 NM	15.6 (14.2–17.1)	0.40	17.1 (15.9–18.3)	0.04	16.3 (15.4–17.3)	0.04
CYP2A6 RM	14.6 (12.9–16.2)		15.4 (13.9–16.9)		14.9 (13.8–16.1)

CYP2A6 NM, predicted normal CYP2A6 metabolic activity; CYP2A6 RM, predicted reduced CYP2A6 metabolic activity.

^aCigarettes per day is not normally distributed and P values were calculated with a non-parametric Wilcoxon rank-sum test.