Table 3.

Association for NAT2 slow acetylation genotype with bladder cancer risk stratified by smoking characteristics, and joint association for cigarette smoking characteristics and NAT2 acetylation genotype with bladder cancer risk compared to never smokers with NAT2 rapid/intermediate acetylation genotype

	Frequencies				NAT2 slow genotype association by smoking		Joint NAT2 slow genotype and smoking association
	NAT2 rapid/inter.		NAT2 slow				NAT2 rapid/inter.		NAT2 slow		p*
Smoking characteristics	cases	controls	cases	controls	OR	(95% CI)	OR	(95% CI)	OR	(95% CI)	interaction
Smoking status †
Never	66	131	91	199	0.9	(0.6-1.3)	1.0		0.9	(0.6-1.3)
Ever	340	362	637	438	1.6	(1.3-1.9)	2.9	(2.0-4.2)	4.6	(3.2-6.6)	0.008
Occasional	16	37	32	48	1.2	(0.6-2.4)	1.2	(0.6-2.4)	1.6	(0.9-2.9)	0.28
Former	161	212	310	240	1.7	(1.3-2.2)	2.4	(1.6-3.7)	4.1	(2.8-6.1)	0.006
Current	163	113	295	150	1.4	(1.1-2.0)	5.2	(3.4-8.0)	7.5	(5.0- 11.3)	0.05
Type of tobacco ‡
Never	66	131	91	199	0.9	(0.6-1.3)	1.0		0.9	(0.6-1.3)
Black	284	272	553	328	1.6	(1.3-2.0)	3.6	(2.4-5.4)	5.9	(4.0-8.7)	0.005
Blond	40	52	52	61	1.2	(0.7-2.1)	2.5	(1.4-4.3)	2.9	(1.7-4.9)	0.36
Smoking intensity §
Never	66	131	91	199	0.9	(0.6-1.3)	1.0		0.9	(0.6-1.3)
< 10 cig/day	26	55	43	61	1.7	(0.9-3.2)	0.6	(0.3-1.1)	0.9	(0.5-1.8)	0.09
10-<20 cig/day	67	57	106	77	1.2	(0.7-1.9)	1.3	(0.7-2.6)	1.6	(0.9-3.0)	0.31
20-<30 cig/day	143	108	263	133	1.4	(1.0-2.0)	1.6	(0.9-2.9)	2.3	(1.3-4.1)	0.05
30-<40 cig/day	31	27	88	42	1.8	(0.9-3.5)	1.4	(0.6-3.0)	2.5	(1.3-4.8)	0.06
≥ 40 cig/day	54	73	102	71	1.7	(1.1-2.8)	1.0	(0.5-2.0)	1.8	(0.9-3.3)	0.03

^*p value for differences between the OR for NAT2 slow acetylation genotype within strata defined by smoking characteristics compared never smokers. This test is equivalent to testing if the observed joint OR for NAT2 slow genotype and smoking characteristics differs from the product of the OR for each factor alone.

^†Odds ratios are from conventional logistic regression models adjusted for gender, age and region.

^‡Black tobacco are “known or likely black tobacco smokers” defined as subjects who smoked black tobacco alone, black and blond tobacco, or unknown tobacco type. Odds ratios are from conventional logistic regression models adjusted for gender, age, region and smoking cessation (former/current). The p for interaction for former versus current smokers is 0.44 and for blond versus black tobacco is 0.33.

^§Odds ratios are from conventional logistic regression models adjusted for age, gender and region, smoking duration (< 20 years, 20-<30 years, 30-<40 years, 40-<50 years, ≥ 50 years) and smoking cessation (current/former).

ORs for NAT2 slow acetylation for different categories of smoking intensity are not significantly different from the highest intensity category (p for interaction for categories <10, 10-<20, 20-<30, 30-<40 cig/day compared to ≥40 cig/day are 0.96, 0.30. 0.58 and 0.90 respectively for total intensity).