Table 2. Cross-sectional study.

		Selection			Comparability	Outcome		Total quality score	Quality
Study	Representativeness of the sample	Sample size	Non-respondents	Ascertainment of the exposure (risk factor)	Confounding factors controlled	Assessment of outcome	Statistical test
Lissauer et al. [21]	1	0	1	2	2	2	1	9	Very good
Rhee et al. [22]	1	0	0	0	0	1	1	3	Unsatisfactory
Wong et al. [23]	1	0	1	1	1	1	1	6	Satisfactory
Herc et al. [24]	1	0	1	2	2	2	1	9	Very good
Kim et al. [25]	1	0	1	2	1	2	1	8	Good
Torre et al. [26]	0	0	0	1	1	2	1	5	Satisfactory
Malek et al. [27]	0	1	1	2	1	2	1	8	Good
Hernández-Aceituno et al. [28]	0	0	1	0	1	1	1	4	Unsatisfactory
DiPietro et al. [29]	1	0	0	2	1	1	1	6	Satisfactory
Ahn et al. [30]	1	0	1	2	2	1	1	8	Good