Table 1

Quantitative studies. Quality assessed using the Standard Quality Assessment Criteria for Evaluating Primary Research Papers from a variety of fields

Authors	Question/objective sufficiently described?	Study design evident and appropriate?	Method of subject/comparison group selection or source of information/input variables described and appropriate?	Subject (and comparison group, if applicable) characteristics sufficiently described?	If interventional and random allocation was possible, was it described?	If interventional and blinding of investigators was possible, was it reported?	If interventional and blinding of subjects was possible, was it reported?	Outcome and (if applicable) exposure measure(s) well defined and robust to measurement/misclassification bias? Means of assessment reported?	Sample size appropriate?	Analytical methods described/justified and appropriate?	Some estimate of variance is reported for the main results?	Controlled for confounding?	Results reported in sufficient detail?	Conclusions supported by the results?	Summary score
An et al21	2	2	2	1	N/A	N/A	N/A	2	2	1	1	2	2	2	0.86	Yes	2
Bükki et al22	2	2	2	2	N/A	N/A	N/A	2	1	2	2	0	2	2	0.86	Partial	1
Davies et al23	2	2	2	1	N/A	N/A	N/A	2	1	2	2	1	1	2	0.82	No	0
Engelberg et al24	2	2	2	2	N/A	N/A	N/A	2	1	2	1	1	2	2	0.86	N/A
Gao et al25	2	2	2	2	N/A	N/A	N/A	2	1	2	1	2	2	2	0.91
Hauke et al26	2	2	2	2	N/A	N/A	N/A	2	1	1	0	1	2	2	0.77
Heyland et al27	2	2	2	2	N/A	N/A	N/A	2	2	2	1	1	2	2	0.91
Heyland et al28	2	2	2	1	N/A	N/A	N/A	2	1	2	2	0	2	0	0.73
Hwang et al29	1	2	2	2	N/A	N/A	N/A	2	1	2	1	1	2	2	0.82
Kim et al30	2	2	2	2	N/A	N/A	N/A	2	1	2	2	2	2	0	0.86
Ozdemir et al31	2	2	2	2	N/A	N/A	N/A	2	1	2	1	2	2	2	0.91
Pruchno et al32	2	2	1	2	N/A	N/A	N/A	2	1	1	2	2	2	2	0.86
Sharma et al33	2	2	2	2	N/A	N/A	N/A	2	1	2	1	2	2	2	0.91
Shin et al34	2	2	2	2	N/A	N/A	N/A	1	2	1	2	2	1	2	0.86
Stajduhar et al35	2	2	2	2	N/A	N/A	N/A	1	1	2	0	2	2	2	0.82
Tang et al36	2	2	2	2	N/A	N/A	N/A	2	2	1	2	2	2	2	0.95
Tobin et al37	2	2	2	2	N/A	N/A	N/A	1	2	2	1	2	2	2	0.91
Wen et al38	2	2	1	2	N/A	N/A	N/A	2	2	2	1	2	2	2	0.91
Yoo et al39	2	2	2	2	N/A	N/A	N/A	1	1	1	2	2	2	2	0.86
Yun et al40	1	2	1	2	N/A	N/A	N/A	2	2	2	2	2	2	2	0.91
Zhang et al41	2	2	1	2	N/A	N/A	N/A	1	2	2	2	2	2	2	0.91

The summary score for each study is derived by calculating the total score of relevant items (ie, all items except those ‘not applicable’) and dividing it by the total possible score when excluding ‘not applicable’ items.
N/A, not applicable.