Table 2.

Summary of pooled relative risks of prostate cancer in subgroups

	No. of studies	RR	95% CI	P for heterogeneity	I2 (%)
All	9	1.07	0.79-1.46	< 0.001	83.4
Region
USA	4	1.54	1.23-1.93	0.259	25.4
Non-USA	5	0.74	0.50-1.09	0.001	78.4
Study type
Prospective cohort study	2	0.80	0.12-5.20	0.057	72.3
Retrospective cohort study	7	1.03	0.75-1.42	< 0.001	82.3
Publication year
Before 2000	5	1.24	0.92-1.67	0.008	70.7
After 2000	4	0.86	0.44-1.70	< 0.001	88.7
Number of adjustment factors
n ≥ 4 confounders	2	1.39	0.93-2.07	0.108	61.3
n ≤ 3 confounders	7	0.98	0.68-1.41	< 0.001	83.0