Table 2.

Quality assessment of included studies

unclear risk of bias, high risk of bias, low risk of bias, Selection Q1: Representativeness of the exposed cohort, Selection Q2: Selection of the non-exposed cohort, Selection Q3: Ascertainment of exposure, Selection Q4: Demonstration that outcome of interest was not present at start of study, Comparability: Comparability of cohorts on the basis of the design or analysis, Outcome Q1: Assessment of outcome, Outcome Q2: Was follow-up long enough for outcomes to occur, Outcome Q3: Adequacy of follow up of cohorts, Analysis: appropriate statistical analysis