Table 3.

Results of assessment of methodological quality of observational studies using standardised critical appraisal instruments from the Joanna Briggs institute

Study	Quality assessment domains
	1	2	3	4	5	6	7	8	9	10	11
de Sousa et al. [52, 38]	1	1	1	1	1	3	1	1	1	2	1
Lai et al. [37, 39]	1	1	1	1	1	3	1	1	1	2	1
Monse et al. [22, 24]	1	1	1	1	2	2	1	2	1	2	2
Yusof et al. [50, 36]	1	1	1	1	1	3	1	1	1	2	1

Key: 1 Yes; 2 No; 3 Unclear

Domain 1: Were the two groups similar and recruited from the same population?

Domain 2: Were the exposures measured similarly to assign people to both exposed and unexposed groups?

Domain 3: Was the exposure measured in a valid and reliable way?

Domain 4: Were confounding factors identified?

Domain 5: Were strategies to deal with confounding factors stated?

Domain 6: Were the participants free of the outcome at the start of the study?

Domain 7: Were the outcomes measured in a valid and reliable way?

Domain 8: Was the follow up time reported and long enough for outcomes to occur?

Domain 9: Was follow up complete, and if not, were the reasons to loss to follow up described and explored?

Domain 10: Were strategies to address incomplete follow up utilized?

Domain 11: Was appropriate statistical analysis used?