Table 2b.

Quality assessment of the included case-control study.

No	The Joanna Briggs Institute checklist question	Cai et al., 2020
1	Were the groups comparable other than the presence of disease in cases or the absence of disease in controls?	Y
2	Were cases and controls matched appropriately?	Y
3	Were the same criteria used for identification of cases and controls?	Y
4	Was exposure measured in a standard, valid and reliable way?	Y
5	Was exposure measured in the same way for cases and controls?	Y
6	Were confounding factors identified?	N
7	Were strategies to deal with confounding factors stated?	N
8	Were outcomes assessed in a standard, valid and reliable way for cases and controls?	Y
9	Was the exposure period of interest long enough to be meaningful?	Y
10	Was appropriate statistical analysis used?	Y
	Overall Appraisal	Include: 8
		Exclude: 2
	Level of evidence	Level 3.d – Case – controlled study

Yes= 1, No = 0.