Fig. 2: Risk of bias assessment of included studies.

− no, + yes, +/− unclear. aAccording to the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Analytical Cross-Sectional Studies21.

− no, + yes, +/− unclear. aAccording to the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Analytical Cross-Sectional Studies21.