Table 7.

Results of quality assessment of 181 studies—case–control studies: 9 studies. The Joanna Briggs Institute Critical Appraisal Checklist is used

Scoring: Yes = 2 / Unclear = 1 / No = 0 / NA = not applicableQ1: Were the groups comparable other than the presence of disease in cases or the absence of disease in controls? Q2: Were cases and controls matched appropriately? Q3: Were the same criteria used for identification of cases and controls? Q4: Was exposure measured in a standard, valid and reliable way? Q5: Was exposure measured in the same way for cases and controls? Q6: Were confounding factors identified? Q7: Were strategies to deal with confounding factors stated? Q8: Were outcomes assessed in a standard, valid and reliable way for cases and controls? Q9: Was the exposure period of interest long enough to be meaningful? Q10: Was appropriate statistical analysis used?
Study (serial no.)	Q1	1. Q2	2. Q3	3. Q4	4. Q5	5. Q6	6. Q7	7. Q8	8. Q9	9. Q10	Total ( /20)	%
15	2	1	2	2	2	1	1	2	2	2	17	85.0
20	1	1	1	2	2	1	1	2	0	2	13	65.0
69	1	1	1	2	2	2	1	2	2	2	16	80.0
93	2	2	2	2	2	0	0	2	2	2	16	80.0
98	2	2	2	2	2	0	0	2	2	2	16	80.0
102	1	1	1	2	2	0	0	2	2	2	13	65.0
108	2	1	1	2	2	1	1	2	1	2	15	75.0
114	2	2	2	2	2	2	2	2	2	2	20	100.0
179	2	2	2	2	2	2	2	2	2	2	20	100.0

Studies are described using Serial numbers in Table 3