Table 4.

Methodological quality of the included studies.

	1a	2b	3c	4d	5e	6f	7g	8h	9i	10j	11k	Total score
Yang et al, 2013 [18]	1	0	1	?l	1	1	1	?	1	1	0	8
Gibbons et al, 2016 [23]	1	1	1	1	1	1	1	?	1	0	0	8
Laver et al, 2017 [19]	1	1	1	1	0	0	1	?	?	0	0	5
Iruthayarajah et al, 2017 [24]	1	0	1	1	1	1	1	?	?	0	0	6
Mohammadi et al, 2019 [25]	1	1	1	1	1	1	1	?	1	0	1	9
Maier et al, 2019 [20]	0	1	0	0	1	1	1	?	1	1	1	6
Zhong et al, 2019 [21]	1	1	1	?	1	1	1	?	1	1	1	7
Domínguez-Téllez et al, 2020 [2]	1	1	1	1	1	1	1	?	1	0	1	9
Liang et al, 2020 [26]	1	1	1	?	1	1	1	?	1	1	0	8
Mekbib et al, 2020 [22]	1	0	1	0	0	0	1	?	1	0	1	5

^aWhether the preliminary design scheme was provided.

^bWhether the included studies and data extraction were repetitive.

^cWhether an extensive and comprehensive literature search was carried out.

^dWhether the publication was considered.

^eWhether the list of included and excluded studies was provided.

^fWhether the characteristics of the included studies were described

^gWhether the scientificity of the included studies was evaluated and reported.

^hWhether the scientificity of the included studies was appropriately used in the derivation of conclusions.

ⁱWhether it was appropriate to summarize the research results.

^jWhether the possibility of publication bias was evaluated.

^kWhether the relevant conflicts of interest were explained.

^lUnknown.