Table 2. Quality assessment of the included cross-sectional studies according to the NOS.

Each * represents a score. * = 1 point and ** = 2 points

Note: A study can be awarded a maximum of one star for each numbered item within the Selection and Exposure categories. A maximum of two stars can be given for Comparability.

Author and year	Cross-sectional studies
	Selection				Comparability	Outcome		Quality score
	Representativeness of the sample	Sample size	Ascertainment of exposure	Non-respondents	The subjects in different outcome groups are comparable based on the study design or analysis. Confounding factors are controlled.	Assessment of the outcome	Reporting the results		Level
Alrahili et al. 2021 [21]	*	*	**	*	*	*	*	7	fair
Hu et al. 2019 [22]	*	*	*	*	*	*	*	6	fair
Md Zaki Fadzil et al. 2020 [23]	*	*	**	*	*	*	*	7	fair
Bibi et al. 2022 [24]	*	*	**	*	*	*	*	7	fair
Hill et al. 2020 [25]	*	*	**	*	*	*	*	7	fair
Wu et al. 2016 [26]	*	*	**	*	*	*	*	7	fair