Table 3. Quality assessment for included studies by the Newcastle-Ottawa Scale (NOS).

Author (Year)	Selection (maximum 4 stars)	Comparability (maximum 2 stars)	Outcome (maximum 3 stars)	Total (maximum 9 stars)
Barger et al. (2005) [18]	***	*	*	*****
Marcus et al. (1996) [19]	**	*		***
O’Grady et al. (2012) [22]	**	*		***
Ware et al. (2006) [17]	*	*	***	*****
Tornero et al. (2012) [16]	*	*	***	*****