Table 1. Assessment of study quality.

Study	Diabetes	Outcome	Loss to follow-up		Major confounders control			Quality
	ascertainment	ascertainment	<20%(PC)	<5%(HC)	HBV	HCV	Alcohol drinking	score
Ikeda Y 1998 [69]	MR or MU	MR	-	Yes	Yes	Yes	No
Fujino Y 2001 [68]	SR	DC	Unknown	-	No	No	Yes	1
Tazawa J 2002 [25]	MR or MU	MR	-	Yes	No	Yes	No	6
Poon RTP 2002 [67]	MR or MU	MR	-	Yes	Yes	No	Yes	7
Huo TI 2003 [66]	MR or MU	MR	-	Yes	Yes	Yes	No	7
Huo TI 2003 [65]	MR or MU	MR	-	No	Yes	No	No	5
El-Serag HB 2004 [24]	MR	MR	-	Yes	No	No	No	3
Huo TI 2004 [62]	MR or MU	MR	-	Yes	Yes	No	No	6
Coughlin SS 2004 [63]	MR or SR	CR	Unknown	-	No	No	Yes	1
Batty GD 2004 [64]	SR	CR	Unknown	-	No	No	No	1
Jee SH 2005 [61]	MR	CR	Unknown	-	No	No	Yes	2
Park SM 2006 [60]	MR or SR	CR	-	Yes	No	No	Yes	2
Inoue M 2006 [23]	SR	MR	Yes	-	No	No	Yes	3
Khan M 2006 [22]	SR	CR	Unknown	-	No	No	Yes	1
Lai MS 2006 [21]	MR	MR	Unknown	-	Yes	Yes	Yes	6
Torisu Y 2007 [20]	MR	MR	-	No	No	No	Yes	3
Komura T 2007 [59]	MR	MR	-	Yes	Yes	Yes	Yes	7
Ioannou GN 2007 [29]	MR	MR	-	Yes	Yes	Yes	Yes	7
Kawamura Y 2008 [57]	MR	MR	-	No	No	No	Yes	3
Di Costanzo GG 2008 [28]	MU or SR	MR	-	Yes	No	No	Yes	5
Veldt BJ 2008 [27]	MR or MU	MR	-	Yes	No	No	Yes	6
Oba S 2009 [58]	SR	CR	Unknown	-	No	No	Yes	1
Ogunleye AA 2009 [19]	DR	CR	Unknown	-	No	No	No	1
Wang CS 2009 [18]	MR	CR	Yes	-	Yes	Yes	No	7
Lam EK 2010 [56]	MR	Unknown	Unknown	-	No	No	No	1
Chodick G 2010 [17]	MR or MU	CR	No	-	No	No	No	2
Hung CH 2010 [26]	MR	DC	-	Yes	Yes	No	Yes	6
Huo TI 2010 [55]	MR or MU	MR	-	Yes	Yes	Yes	No	7

Abbreviations: CR, cancer registry; DC, death certificate; DR, diabetes registry; HC, hospital-based cohort study; MR, medical record; MU, medication use; PC, population-based cohort study; SR, self-report.