Fig. 3

Risk-of-bias assessment using the revised Risk of Bias Assessment tool for Non-randomized Studies (RoBANS2). Green (+) indicates low risk of bias; yellow (-) indicates unclear risk of bias; and red (×) indicates high risk of bias. For the summary of risk of bias, studies were considered to have an overall low risk of bias (green +) if they were classified as low risk in all eight domains. Studies were considered to have an unclear risk of bias (yellow -) if at least one domain was rated as unclear risk (but no domains were rated as high risk) and as high risk (red ×) if at least one domain was rated as high risk