Table 3.

Newcastle-Ottawa scale for risk of bias assessment of the studies included in the meta-analyses.

Quality assessment criteria	Acharya et al. (2017)	Bajaj et al. (2011)	Bajaj et al. (2013)	Garcia-Martinez et al. (2011)	Hopp et al. (2019)	Nardelli et al. (2017)	Riggio et al. (2011)	Sotil et al. (2009)	Umapathy et al. (2014)	Zarantonello et al. (2019)
Selection
Representativeness of exposed cohort	*	*	*	*	*	*	*	*	*	*
Selection of the non-exposed cohort	*	*	*	*	*	*	*	*	*	*
Ascertainment of exposure	*	*	*	*	*	*	*	*	*	*
Demonstration that outcome of interest was not present at start of study	–	*	–	-	–	-	–	-	–	–
Comparability
Study controls adjusted for main factor?	*	*	*	*	*	*	*	*	*	*
Study controls adjusted for additional factors?	*	–	*	*	*	–	*	*	–	*
Outcome
Assessment ofoutcome	*	*	*	*	*	*	*	*	*	*
Was follow-up longenough for outcometo occur (2 years)	*	*	*	*	*	*	*	*	*	*
Adequacy offollow-up ofcohorts? (80%)	*	*	*	*	*	*	*	*	*	*
Overall Quality Score (Maximum: 9)	8	8	8	8	8	7	8	8	7	8

The studies receiving at least six stars (maximum of nine) were classified as good quality.