Table 4

Incidence RR^a of bladder cancer according to toenail selenium levels by category of vitamin intake; Netherlands Cohort Study (1986–1992)

Group	No. of cases	Quintile of toenail selenium (boundaries in μg/g)							P-trend
Group	No. of cases			1 (≤0.483)	2 (≤0.530)	3 (≤0.573)	4 (0.630)	5 (>0.630)	P-trend
β-Carotene intake^b
Low	167	1.00 (reference)	0.98 (0.59–1.62)	0.50 (0.28–0.89)	0.71 (0.40–1.26)	0.65 (0.36–1.16)	0.02
High	155	1.00 (reference)	1.08 (0.65–1.80)	0.97 (0.55–1.71)	0.66 (0.34–1.26)	0.74 (0.41–1.34)	0.09
Vitamin C intake^b
Low	181	1.00 (reference)	0.95 (0.59–1.53)	0.45 (0.26–0.78)	0.72 (0.41–1.26)	0.77 (0.43–1.37)	0.05
High	140	1.00 (reference)	1.09 (0.64–1.85)	1.01 (0.57–1.80)	0.50 (0.25–1.00)	0.75 (0.41–1.37)	0.06
Vitamin E intake^b
Low	145	1.00 (reference)	1.37 (0.81–2.33)	0.58 (0.30–1.09)	0.76 (0.41–1.42)	0.82 (0.45–1.50)	0.07
High	170	1.00 (reference)	1.09 (0.68–1.75)	0.59 (0.34–1.03)	0.70 (0.38–1.28)	0.73 (0.41–1.29)	0.04

^a Adjusted for age (years), sex, number of cigarettes/day, and years of cigarette smoking.
^b Low and high are defined as the two lowest quintiles and the two highest quintiles of intake, respectively. For β-carotene, the cutoff values for low and high were: ≤2.36, >2.97 mg/day; for vitamin C the corresponding values were ≤86.60 and >107.71 mg/day, and for vitamin E the corresponding values were ≤10.72 and <13.89 mg/day. The Ps for interaction were 0.58, 0.16, and 0.96 for β-carotene, vitamin C, and vitamin E.