Table S1. Methodological quality of cohort studies included in the meta-analysis*.

Reference (first author, year)	Representativeness of exposed cohort	Selection of unexposed cohort	Ascertainment of exposure	Outcome of interest not present at start of study	Control for important factor or additional factor†	Outcome assessment	Follow-up long enough for outcomes to occur‡	Adequacy of follow-up of cohorts	Total quality scores
Sinn, 2012	–	☆	☆	☆	☆☆	☆	–	☆	7
Kusakabe, 2011	☆	☆	☆	☆	☆☆	☆	☆	☆	9
Yuen, 2009	–	☆	☆	☆	☆☆	☆	–	☆	7
Fang (b), 2008	☆	☆	☆	☆	☆	☆	–	☆	7
Yang, 2008	☆	☆	☆	☆	☆☆	☆	☆	☆	9
Chen, 2007	–	☆	☆	☆	☆☆	☆	☆	☆	8
Jang, 2007	–	☆	☆	–	–	☆	☆	☆	5
Tong, 2006	–	☆	☆	☆	–	☆	–	–	4

*, a study could be awarded a maximum of one star for each item except for the item Control for important factor or additional factor; ^†, a maximum of 2 stars could be awarded for this item. Studies that matched or controlled for age and sex received one star, whereas studies that controlled for more than 3 of other important confounders such as alcohol drinking, smoking, HBV DNA, Genotype, HBeAg, ALT, liver cirrhosis received an additional star; ^‡, a cohort study with a follow-up time >10 year was assigned one star.