Supplementary File 4.

Results of study quality assessment using Newcastle-Ottawa Scale tools

Case control
First author, year of publication, country	Selection 1: Is the case definition adequate?	Selection 2: Representativeness of the cases	Selection 3: Selection of controls	Selection 4: Definition of controls	Comparability of cases and controls on the basis of the design or analysis	Exposure 1: Ascertainment of exposure	Exposure 2: Same method of ascertainment for cases and controls	Exposure 3: Nonresponse rate	Overall risk of bias
Yang et al., 2015 [19]	*	*	*	*	**	*	0	*	Good quality
Astorri et al., 2010 [24]	*	*	*	*	**	*	*	0	Good quality
Albadr and Haddad, 2023 [21]	*	*	0	*	**	*	0	*	Good quality
Cross sectional
First author, year of publication, country	Selection 1: Representativeness of the sample	Selection 2: Sample size	Selection 3: Nonrespondents	Selection 4: Ascertainment of the exposure		Comparability 1: Potential cofounding factor	Outcome 1: Assessment of outcome	Outcome 2: Statistical test	Overall risk of bias
Li et al., 2017 [25]	0	*	*	**		**	**	*	Very good quality
Zhu et al., 2020 [27]	*	0	0	**		**	**	*	Good quality
Sobajima et al., 1998 [23]	*	0	0	**		0	**	*	Satisfactory quality
Zhi et al., 2016 [26]	*	0	0	**		0	**	*	Satisfactory quality

All risk-of-bias evaluations were conducted according to the Newcastle-Ottawa Scale (NOS) adapted for cross-sectional or case-control study guidelines. Applied for both NOS types, 2 stars (**) are awarded if all or most of the requirements are fulfilled in each section, and 1 star (*) is given if only half of the requirements are fulfilled, or if the question is answered but not sufficiently. No star (0) is assigned if no information is provided or if there is no description at all.