	Quartiles of serum GPx3 activity (units/L)				Continuous (per 100 units/L)
	<589	589-655	655-715	≥715	Continuous (per 100 units/L)
Cases/controls (n)	70/121	65/125	48/123	65/123	0.29
		0.57	0.07	0.68	0.93
Crude OR^* (95% CI)	1.00	0.89 (0.58, 1.35)	0.67 (0.43, 1.04)	0.92 (0.60, 1.40)	(0.81, 1.07)
		0.36	0.05	0.46	0.17
Adjusted OR^† (95% CI)	1.00	0.82 (0.53, 1.26)	0.63 (0.39, 0.99)	0.85 (0.55, 1.31)	0.91 (0.79, 1.04)
Excluding cases diagnosed during 1st year of follow-up (and matched controls)
Cases/controls (n)	68/116	63/116	44/119	60/155
Adjusted OR^† (95% CI)	1.00	0.84 (0.54, 1.31)	0.59 (0.36, 0.94)	0.83 (0.53, 1.30)	0.88 (0.76, 1.02)
High-grade prostate cancer
Cases/controls (n)	27/45	26/48	21/44	18/45
Adjusted OR^† (95% CI)	1.00	0.86 (0.43, 1.73)	0.82 (0.41, 1.65)	0.68 (0.33, 1.40)	0.85 (0.67, 1.09)
Low-grade prostate cancer
Cases/controls (n)	39/66	32/65	23/66	36/61
Adjusted OR^† (95% CI)	1.00	0.74 (0.40, 1.36)	0.50 (0.25, 0.99)	0.80 (0.42, 1.52)	0.90 (0.74, 1.10)

↵*Crude OR from conditional logistic regression stratified by matching factors (age group and time of recruitment).
↵^†Adjusted OR additionally adjusted for family history of prostate cancer, participation in PSA testing, smoking status, and vigorous physical activity.