Table 2.

NOS for the risk of bias and quality assessment of NRSs.

Author	Year	Selection				Comparability	Exposure			Total Score
		Adequate Definition of Patient Cases	Representativeness of Patient Cases	Selection of Controls	Definition of Controls	Control for Important or Additional Factors	Ascertainment of Exposure	Same method of Ascertainment for Participants	Nonresponse Rate
Fabian [6]	1993	⋆	⋆	⋆			⋆	⋆		5
Townsend [7]	1993	⋆	⋆	⋆			⋆	⋆		5
Taner [8]	2001	⋆	⋆	⋆	⋆	⋆	⋆	⋆		7
Mathonnet [9]	2003	⋆	⋆	⋆			⋆	⋆		5
Omori [10]	2003	⋆	⋆	⋆	⋆	⋆	⋆	⋆		7
Mitsuhide [11]	2005	⋆	⋆	⋆			⋆	⋆		5
Huscher [12]	2006	⋆	⋆	⋆			⋆	⋆		5
Kaban [13]	2008	⋆	⋆	⋆	⋆	⋆	⋆	⋆		7
Mallat [14]	2008	⋆	⋆	⋆	⋆		⋆	⋆		6
Shah [15]	2011	⋆	⋆	⋆			⋆	⋆		5
Johnson [16]	2013	⋆	⋆	⋆	⋆	⋆	⋆	⋆		7
Memon [18]	2013	⋆	⋆	⋆			⋆	⋆		5
Khubutiya [17]	2013	⋆	⋆	⋆	⋆		⋆	⋆		6
Huang [19]	2017	⋆	⋆	⋆	⋆	⋆	⋆	⋆		7
Koto [23]	2018	⋆	⋆	⋆			⋆	⋆		5
Parajuli [22]	2017	⋆	⋆	⋆	⋆	⋆	⋆	⋆		7
Lin [20]	2018	⋆	⋆	⋆	⋆	⋆	⋆	⋆		7
Matsevych [21]	2018	⋆	⋆	⋆	⋆	⋆	⋆	⋆		7
Nicolau [24]	2019	⋆	⋆	⋆	⋆	⋆	⋆	⋆		7

NOS, Newcastle-Ottawa scale; NRS, non-randomized study; ⋆, The study has met the criteria for a domain of the Newcastle-Ottawa Scale.