- The first four Cochrane risk of bias assessment features are not relevant for non-RCTs, since all of the included studies were non-RCTs these were not assessed (random sequence generation, allocation concealment, blinding of participants and personnel, and blinding of outcome assessment)
- aAttrition bias due to amount, nature or handling of incomplete outcome data
- bReporting bias due to selective outcome reporting
- cBias due to problems not covered elsewhere in the table
- note: green cells indicate "low risk" of bias, yellow cells indicate "unclear risk" of bias, and red cells indicate "high risk" of bias
