Table 3.

Risk of bias assessment based on Downs and Black’s criteria¹⁶

Author	Year	Reporting	Internal validity	Confounding and selection bias	External validity	Power	Total score
Banerjee et al*9	2020						18
Campbell et al23	2016						12
Chigbu et al*18	2020						17
Duan et al*28	2021						21
Eakin et al24	2018						17
Fokom Domgue et al25	2020						14
Joshi et al26	2015						20
Joshi et al*10	2013						17
Mungo et al*19	2020						19
Naud et al*22	2016						14
Pinder et al*11	2020						24
Sandoval et al*20	2019						20
Viviano et al*21	2017						21
Zhao et al*12	2021						19
Zhao et al27	2020						20

Subsections were scored green if over 80% of indicators met, orange if 40%–79% of indicators met and red if <40% of indicators met.

*Included in the meta-synthesis.