Table 4.

Quality evaluation of the included studies for the meta-analysis.

	Quality (NOS)
Study	Selection (4*)	Comparability (3*)	Exposure (2*)
Huang et al. (19)	****		**
Valentino, 2017 (30)	***	**	**
Majed et al. (13)	**		**
Liang et al. (26)	****	*	**
Kovacs et al. (20)	****		**
Jarius et al. (12)	***		**
Jarius et al. (16)	***		**
Isobe et al. (25)	***		**
Isobe et al. (29)	****		**
Chanson (31)	****	**	**
Akaishi et al. (24)	**	*	**
Takahashi et al. (15)	***	*	**
Dujmovic et al. (22)	***	*	**
Li et al. (21)	***		**

Each study is scored using a star system based on three domains: (1) selection of study groups—maximum 4*; (2) comparability of the groups—maximum 2*; (3) ascertainment of outcome—maximum 3*. NOS, Newcastle–Ottawa Scale.