Study Type of study Selection Comparability Outcome/exposure Overall
Madasu et al. Cohort 2 (*) 1 (*) 0 (*) Poor Quality
Scasso et al. Case and controls 3 (*) 0 (*) 1 (*) Poor Quality
Fernandez et al. Cohort 3 (*) 1 (*) 3 (*) High Quality
Ishikawa et al. Cohort 3 (*) 1 (*) 3 (*) High Quality
Ekborn et al. Cohort 2 (*) 0 (*) 1 (*) Poor Quality