Table 1.

Summary of results from the seven eligible studies on selenium and bladder cancer risk.

First author, year	Country	Matrix	Sex	Cases	Controls	Selenium concentration	OR	95% CI	P-trend	Smoker	Adjustment
Case-control
Helzlsouer, 1989 (17)	U.S.A.	Serum	Combined sexes	14	23	<110 μg/L	1.00		0.03	Undefined	Age, sex, race, blood collection, previous meal
				14	23	110–119 μg/L	0.51	0.15–1.75
				7	24	>119 μg/L	0.49	0.16–1.49
Kellen, 2006 (18)	Belgium	Serum	Combined sexes	109	120	1.60–82.39 μg/L	1.00		<0.001	Undefined	Age, sex, smoking, occupation, PAHs or AA
				41	120	82.40–95.99 μg/L	0.48	0.29–0.79
				28	122	≥96.00 μg/L	0.30	0.17–0.51
Wallace, 2009 (22)	U.S.A.	Toenails	Combined sexes	245	280	<0.77 μg/g	1.00		0.15	Undefined	Age, sex, smoking
				217	275	0.77–0.86 μg/g	1.04	0.79–1.35
				138	276	0.87–0.95 μg/g	0.73	0.55–0.98
				167	277	>0.95 μg/g	0.90	0.68–1.19
			Men	n.a.	n.a.	<0.77 μg/g	1.00		0.35	Undefined	Age, smoking
				n.a.	n.a.	0.77–0.86 μg/g	1.27	0.93–1.71
				n.a.	n.a.	0.87–0.95 μg/g	0.83	0.59–1.16
				n.a.	n.a.	>0.95 μg/g	0.97	0.70–1.36
			Women	n.a.	n.a.	<0.77 μg/g	1.00		0.11	Undefined	Age, smoking
				n.a.	n.a.	0.77–0.86 μg/g	0.53	0.30–0.93
				n.a.	n.a.	0.87–0.95 μg/g	0.50	0.29–0.84
				n.a.	n.a.	>0.95 μg/g	0.66	0.40–1.10
			Combined sexes	n.a.	n.a.	<0.77 μg/g	1.00		0.12	Never	Age, sex
				n.a.	n.a.	0.77–0.86 μg/g	1.05	0.59–1.88
				n.a.	n.a.	0.87–0.95 μg/g	0.53	0.29–1.00
				n.a.	n.a.	>0.95 μg/g	0.78	0.44–1.37
				n.a.	n.a.	<0.77 μg/g	1.00		0.004	Moderate	Age, sex
				n.a.	n.a.	0.77–0.86 μg/g	0.85	0.56–1.31
				n.a.	n.a.	0.87–0.95 μg/g	0.45	0.28–0.72
				n.a.	n.a.	>0.95 μg/g	0.61	0.39–0.96
				n.a.	n.a.	<0.77 μg/g	1.00		0.009	Heavy	Age, sex
				n.a.	n.a.	0.77–0.86 μg/g	1.09	0.73–1.64
				n.a.	n.a.	0.87–0.95 μg/g	1.30	0.83–2.01
				n.a.	n.a.	>0.95 μg/g	1.44	0.91–2.27
Nested case-control
Nomura, 1987 (16)	U.S.A.	Serum	Men	6	26	<103.1 μg/L	1.00		0.12	Undefined	Age, smoking
				6	50	103.1–112.0 μg/L	0.53	0.15–1.81
				5	76	112.1–123.0 μg/L	0.91	0.26–3.24
				7	59	123.1–133.0 μg/L	0.53	0.16–1.73
				5	82	≥133.1 μg/L	0.31	0.09–1.10
Michaud, 2002 (20)	Finland	Toenails	Men	44	43	1st tertile	1.00		0.79	Ever	Age, nail collection, intervention group
				47	43	2nd tertile	0.88	0.47–1.68
				42	47	3rd tertile	0.90	0.45–1.78
Michaud, 2005 (19)	U.S.A.	Toenails	Men	52	55	0.660 μg/g	1.00		0.61	Undefined	Age, sex, smoking, nail collection
				54	57	0.765 μg/g	1.09	0.59–2.01
				53	55	0.863 μg/g	1.09	0.59–2.00
				62	56	0.990 μg/g	1.17	0.66–2.07
			Women	37	28	0.626 μg/g	1.00		0.02	Undefined	Age, sex, smoking, nail collection
				35	31	0.716 μg/g	0.73	0.35–1.55
				23	29	0.800 μg/g	0.49	0.21–1.16
				21	29	0.933 μg/g	0.36	0.14–0.91
Case-cohort
Zeegers, 2002 (21)	The Netherlands	Toenails	Combined sexes	114	2986	≤0.483 μg/g	1.00		<0.01	Undefined	Age, sex, smoking
				116	3022	0.483–0.530 μg/g	1.09	0.80–1.48
				78	3031	0.531–0.573 μg/g	0.55	0.38–0.79
				62	2993	0.574–0.630 μg/g	0.63	0.43–0.91
				61	3001	>0.630 μg/g	0.67	0.46–0.97
				n.a.	n.a.	≤0.483 μg/g	1.00		0.62	Never	Age, sex, smoking
				n.a.	n.a.	0.483–0.530 μg/g	2.69	1.02–7.09
				n.a.	n.a.	0.531–0.573 μg/g	1.37	0.50–3.79
				n.a.	n.a.	0.574–0.630 μg/g	1.09	0.38–3.14
				n.a.	n.a.	>0.630 μg/g	1.36	0.50–3.69
				n.a.	n.a.	≤0.483 μg/g	1.00		<0.01	Former	Age, sex, smoking
				n.a.	n.a.	0.483–0.530 μg/g	0.74	0.46–1.19
				n.a.	n.a.	0.531–0.573 μg/g	0.48	0.28–0.81
				n.a.	n.a.	0.574–0.630 μg/g	0.49	0.29–0.83
				n.a.	n.a.	>0.630 μg/g	0.44	0.26–0.75
				n.a.	n.a.	≤0.483 μg/g	1.00		0.25	Current	Age, sex, smoking
				n.a.	n.a.	0.483–0.530 μg/g	1.36	0.86–2.14
				n.a.	n.a.	0.531–0.573 μg/g	0.45	0.24–0.86
				n.a.	n.a.	0.574–0.630 μg/g	0.76	0.39–1.47
				n.a.	n.a.	>0.630 μg/g	1.13	0.56–2.27

n.a. = not available