Table 4.

Risk of bladder cancer stratified by education among females in northern New England.

Education level	No College Degree		College Degree		p-interaction
	Ca/Co	OR* (95% CI)	Ca/Co	OR* (95% CI)
Hair dye use
Never**	88/75	Ref	19/40	Ref
Ever	126/185	0.6 (0.4, 0.8)	33/50	1.9 (0.8, 4.4)	0.012
Color
Blonde	54/66	0.7 (0.4, 1.1)	12/18	2.0 (0.7, 6.1)
Red	19/40	0.4 (0.2, 0.7)	3/10	0.8 (0.2, 4.3)
Brown	41/64	0.6 (0.3, 1.0)	14/17	1.8 (0.7, 5.0)
Black	6/9	0.6 (0.2, 1.9)	1/4	--	0.214
Depth of color
Light Blonde	38/45	0.7 (0.4, 1.2)	11/11	3.4 (1.0, 11.9)
M/D Bl, L Br/R	37/51	0.6 (0.4, 1.1)	3/12	0.5 (0.2, 3.3)
M/D Brwn/Red	39/74	0.4 (0.2, 0.7)	15/22	1.8 (0.6, 4.9)
Black	6/9	0.6 (0.2, 1.9)	1/4	--	0.078
Product type
Temporary	18/22	0.7 (0.4, 1.5)	1/3	--
Semi-permanent	43/57	0.7 (0.4, 1.1)	6/25	0.7 (0.2, 2.3)
Permanent	61/102	0.5 (0.3, 0.7)	25/21	3.3 (1.2, 8.9)	0.0004
Dark Permanent	30/70	0.4 (0.2, 0.6)	15/14	2.8 (0.9, 8.7)	0.0006
Exclusive Permanent	50/87	0.5 (0.4, 0.7)	22/13	4.9 (1.7, 14.6)	<0.0001
Age at first use
≤30	58/67	0.7 (0.4, 1.1)	8/15	1.5 (0.4, 5.0)
>30–45	39/70	0.5 (0.3, 0.8)	17/17	3.2 (1.1, 9.2)
>45	29/48	0.6 (0.3, 1.0)	8/18	1.1 (0.3, 3.5)	0.014
Year of first use
< 1980	79/108	0.5 (0.3, 0.9)	15/19	2.0 (0.8, 5.2)
≥ 1980	47/77	0.6 (0.3, 1.0)	18/31	1.8 (0.6, 4.9)
Duration of use
<10	52/68	0.7 (0.4, 1.2)	16/19	2.0 (0.7, 5.9)
10–19	24/46	0.4 (0.2, 0.8)	6/23	0.7 (0.2, 2.3)
20+	49/69	0.5 (0.3, 0.9)	10/7	3.8 (1.1, 13.0)	0.070
Lifetime applications
<50	36/49	0.7 (0.4, 1.3)	14/13	2.8 (0.9, 9.0)
50–99	19/27	0.6 (0.3, 1.3)	5/17	0.9 (0.2, 3.8)
100+	59/94	0.5 (0.3, 0.8)	10/16	1.5 (0.5, 4.4)	0.116

^*Adjusted for age, race, state, smoking.

^**Never users of hair dye are the referent category for each model