Table 3. Risk assessment of the included studies of this systematic review.

First author	Were adequate eligibility criteria developed and applied?	Was the measurement of both exposure and outcomes adequate?	Was confounding adequately controlled for?	Was the follow-up complete and adequate in duration?	Are reports of the study free of suggestion of selective outcome reporting?	Was the study free of other problems that put it at a high risk of bias?	Risk of bias
Bidard [33]	Yes	Yes	Yes	Yes	Yes	Yes	Low
De Albuquerque [34]	Yes	Yes	Yes	Yes	Yes	Yes	Low
Effenberger [35]	Yes	Yes	Yes	Yes	Yes	Yes	Low
Hoffmann [36]	Yes	No	Yes	Unclear	Yes	Yes	High
Hu [37]	Yes	Yes	Yes	Yes	Yes	Yes	Low
Juhl [38]	Yes	Yes	Yes	Yes	Yes	Yes	Low
Khoja [39]	Yes	Yes	Yes	Yes	Yes	Yes	Low
Klos [40]	Yes	Yes	Yes	Yes	No	Yes	High
Kurihara [41]	Yes	Yes	Yes	Yes	Yes	Yes	Low
Rehders [42]	Yes	Yes	Yes	Yes	No	Yes	High
Roder [43]	Yes	Yes	No	No	No	Yes	High
Sergeant [44]	Yes	Yes	Yes	Yes	Yes	Yes	Low
Soeth [45]	Yes	Yes	Yes	Yes	Yes	Yes	Low
van Heek [46]	No	Yes	No	Yes	Yes	Yes	High
Vogel [47]	Yes	Yes	Yes	Yes	Yes	Yes	Low
Zhang [48]	Yes	No	Yes	No	No	Yes	High