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Table 2 Quality assessment of cohort studies included in this meta- analysis 1

From: Consumption of coffee associated with reduced risk of liver cancer: a meta-analysis

Study Representativeness of the exposed cohort Selection of the unexposed cohort Ascertainment of exposure Outcome of interest not present at start of study Control for important factor or additional factor2 Outcome assessment Follow-up long enough for outcomes to occur3 Adequacy of follow-up of cohorts4 Total quality scores
Shimazu et al. [20], 2005 9
Shimazu et al. [20], 2005 9
Inoue et al. [21], 2005 - 7
Kurozawa et al. [22], 2005 - 8
Hu et al. [23], 2008 9
Inoue et al. [24], 2009 - 8
Johnson et al. [25], 2011 - 7
  1. 1A study can be awarded a maximum of one star for each numbered item except for the item Control for most important factor or second important factor.
  2. 2 A maximum of two stars can be awarded for Control for most important factor or second important factor. Studies that controlled for HBV or HCV infection received one star, whereas studies that controlled for alcohol drinking received one additional star.
  3. 3 A cohort study with a follow-up time > 7 y was awarded one star.
  4. 4 A cohort study with a follow-up rate > 75% was awarded one star.