“…Critical risk of bias was found for confounding with 12 studies, 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 that did not adjust for confounding given an overall score assessment of very high risk using ROBINS-E. An additional study 15 scored very high risk due to lack of confounding variables. Ten studies were marked as high risk of bias, six 41 , 42 , 43 , 44 , 45 , 46 of which failed to control for adequate confounding variables and four 47 , 48 , 49 , 50 which failed to sufficiently define their exposure variables.…”