Table 2. Stratified analyses of phosphodiesterase type 5 inhibitors associated with malignant melanoma.

	RR (95% CI)	No. of reports	I2(%)	PHeterogeneity
Study regions
US	1.27(0.72,2.26)	2	76	0.04
Europe	1.13(1.06,1.21)	4	5	0.37
Study design
Cohort	1.18(1.03,1.36)	3	23	0.27
Case–control	1.09(0.98,1.20)	3	64	0.06
Study quality
High (8-9)	1.18(1.03,1.36)	3	23	0.27
Low (≤7)	1.09(0.98,1.20)	3	64	0.06
Case numbers
≥500	1.10(1.02,1.19)	4	51	0.11
<500	1.36(0.91,2.04)	2	51	0.15
Types of drugs
Sildenafil	1.28(1.14,1.44)	5	32	0.20
Vardenafil or tadalafil	1.28(0.93,1.76)	4	70	0.04
Adjustment for sun exposure
Yes	1.84(1.04,3.26)	1	NA	NA
No	1.10(1.03,1.18)	5	39	0.16