Quality Assessment of the Nine Included Studies.

*1 indicates case definition or ascertainment of exposure; 2, representativeness of the cases or exposed cohort; 3, selection of controls or non-exposed cohort; 4, description of the control source or demonstration of outcome of interest in cohort; 5A, based on the most important factor to select and study controls; 5B, based on a second crucial factor to select and study controls; 6, assessment of exposure or outcome by blinded interview or record; 7, same method of ascertainment used for cases and controls or adequate follow-up period; 8, evenly distributed non-response rate or adequacy of follow-up of cohortsQuality Assessment of the Nine Included Studies.