Table 2.

Stratified summary odds ratios (ORs) and corresponding 95% confidence intervals (95% CI) for the association between selenium concentrations and bladder cancer risk (random effects model).

	OR (95% CI)		I2 (p-value)	Publication biasb (p-value)
	Reference	Exposeda
Sexc
Men (n = 4)	1	0.95 (0.69–1.27)	16.2% (0.311)	−1.56 (0.314)
Women (n = 2)	1	0.55 (0.32–0.95)	23.7% (0.252)	---
Sample specimen
Toenails (n = 4)	1	0.81 (0.66–1.00)	0.0% (0.617)	−0.38 (0.751)
Serum (n = 3)	1	0.33 (0.21–0.51)	0.0% (0.728)	0.77 (0.576)
Smoking statusd
Never (n = 2)	1	0.89 (0.55–1.44)	0.0% (0.333)	---
Ever (n = 3)	1	0.85 (0.54–1.34)	0.0% (0.861)	−1.84 (0.507)
Study design
Case-control (n = 3)	1	0.53 (0.23–1.20)	84.8% (0.001)	−3.07 (0.518)
Nested case-control (n = 3)	1	0.70 (0.40–1.21)	6.2% (0.344)	−2.62 (0.323)
Case-cohort (n = 1)	1	0.67 (0.47–0.96)	---	---

n, number of studies considered.

I², degree of heterogeneity.

^atop category of exposure to selenium presented in each study, according to each stratum of sex, matrix, smoking status, and study design.

^bcoefficient from Egger’s test for publication bias.

^cStudies with specific data for men: Nomura et al. 1987 (16), Michaud et al. 2002 (20), Michaud et al. 2005 (19), Wallace et al. 2009 (22); studies with specific data for women: Michaud et al. 2005 (19), Wallace et al. 2009 (22).

^dStudies with specific data for never smokers: Zeegers et al. 2002 (21), Wallace et al. 2009 (22); studies with specific data for ever smokers: Michaud et al. 2002 (19), Zeegers et al. 2002 (21), Wallace et al. 2009 (22).