Table 1.

Study characteristics of included cohort and case–control studies on insulin use and CRC risk

Study, Year	Study period	Study design	Country	No. of participants	No. of cases	Duration of insulin use	Gender	Confounders for adjustment
Campbell 2010 [17]	1992-2007	Cohort	USA	184,194	2,474	≥4 years	M/F	1, 3, 4, 5, 6, 7, 8, 20
Carstens 2012 [18]	1995-2009	Cohort	Denmark	22,826	320	NR	M/F	1, 9, 10
Chang 2012 [19]	2000-2007	C-C	China	108,920	468	≥2 years	M/F	11, 12, 13, 14, 15, 16, 17
Chung 2008 [20]	2003-2006	C-C	Korea	325	100	NR	M/F	1, 2
Currie 2009 [21]	2000–2009	Cohort	UK	62,809	292	NR	M/F	1, 2, 18, 19
Gu 2013 [22]	2001-2010	Cohort	China	8,774	31	NR	M/F	1,2, 11, 18,
Hsieh 2012 [23]	2000-2008	C-C	China	61,777	1,739	NR	M/F	1, 2
Koro 2007 [24]	1997–2004	C-C	USA	2,435	408	NR	M/F	1, 2, 9, 10
Onitilo 2013 [25]	1995-2009	Cohort	USA	9,486	106	NR	M/F	1, 3, 11, 12
Vinikoor 2009 [26]	1996-2006	C-C	USA	3,752	1,688	≥1 years	M/F	1,2, 5, 7, 20, 21
Wong 2012 [27]	1998-2007	C-C	USA	1,168	196	≥3 years	M/F	1, 2
Yang 2004 [28]	1987-2002	C-C	UK	24,918	125	≥5 years	M/F	2, 3, 5, 8, 11, 18

C-C: Case–control study; M: male; F: female.

The adjusteted factors are: (1) age, (2) gender, (3) body mass index, (4) physical activity, (5) nonsteroidal anti-inflammatory drug use, (6) alcohol use, (7) family history of colorectal cancer, (8) endoscopy history, (9) current date of follow-up; (10) date of birth (11) use of sulfonylurea, glinides, metformin, thiazolidinediones, α-glucosidase inhibitors (11) chronic liver disease, (12) nephropathy, (13) statins, β-blocker, calcium channel blockers, (14) cerebrovascular disease, (15) angiotensin-converting enzyme inhibitors, (16) chronic kidney disease, (17) aspirin, (18) smoking status, (19) diagnosis of a previous cancer; (20) education; (21), calcium intake.