Association between oral contraceptive use and pancreatic cancer risk: A systematic review and meta-analysis

Table 2 Association between the use of oral contraceptives and risk of pancreatic cancer: Subgroup analysis

Characteristic	Subgroup	Number of studies	RR (95%CI)	I2 within each subgroup	Test for subgroups differences
Study design	Case-control	10	0.85 (0.64-1.14)	60% (P = 0.008)	P = 0.92
	Cohort	11	0.84 (0.70-1.00)	85% (P < 0.00001)
Source of controls in case-control studies	Population	6	0.75 (0.47-1.21)	63% (P = 0.02)	P = 0.47
	Hospital	4	0.94 (0.64-1.39)	61% (P = 0.06)
Number of pancreatic cancer cases	< 200	8	0.80 (0.56-1.14)	66% (P = 0.004)	P = 0.77
	≥ 200	13	0.85 (0.71-1.00)	83% (P < 0.00001)
Assessed study quality	NOS ≤ 7	9	0.93 (0.75-1.17)	56% (P = 0.02)	P = 0.33
	NOS > 7	12	0.80 (0.66-0.98)	84% (P < 0.00001)
Geographic region1	Europe	7	0.67 (0.51-0.88)	55% (P = 0.04)	P = 0.07
	Americas	10	0.91 (0.74-1.11)	86% (P < 0.00001)
	Asia	3	1.14 (0.76-1.73)	27% (P = 0.25)
Menopausal status	Premenopausal	1	0.90 (0.68-1.19)	N/A	0.90
	Postmenopausal	4	0.88 (0.79-0.98)	17% (P = 0.31)

¹One study was multicentric and conducted in all three geographic regions so it was not included in the subgroup analysis by geographic region.

CI: Confidence interval; NOS: Newcastle-Ottawa Scale; RR: Relative risk.