Table 2.

Quality assessments of included studies.

Study	Case definition adequate	Representativeness of the cases	Selection of Controls	Definition of Controls	Comparability of cases and controls	Ascertainment of exposure	Same method of ascertainment	Non-response rate	Nos
Sakhr (2020; Egypt)	*	*	*	–	**	*	*	*	8
Hawari (2020; Syria)	*	*	*	*	–	*	*	*	7
Yang (2019; China)	*	*	*	*	*	*	*	*	8
Tinkov (2019; Russia)	*	*	*	*	**	*	*	*	9
Avval (2019; Iran)	*	*	–	*	**	–	*	*	7
Abdelnaby (2018; Egypt)	*	*	–	*	–	*	*	*	6
Elbaz (2017; Egypt)	*	*	–	*	**	–	*	*	7
Viktorinova (2016; Slovakia)	*	*	*	*	–	*	*	*	7
Sandyk (1990; Israel)	*	*	*	*	*	*	*	*	8
Bekaroglu (1996; Turkey)	*	*	*	*	–	*	*	*	7
Mahmoud (2011; Egypt)	*	*	*	*	**	*	*	*	9
Antalis (2006; USA)	*	*	*	*	**	*	*	*	9
Khan (2017; KSA)	*	*	*	*	**	*	*	*	9
Yorbik (2008; Turkey)	*	*	*	*	–	*	*	*	7
Tinkov (2020; Russia)	*	*	*	*	**	*	*	*	9
Skalny (2020; Russia)	*	*	*	*	**	*	*	*	9
Perham (2020; NewZealand)	*	*	*	*	**	*	*	*	9
Setiawati (2019; Indonesia)	*	*	*	*	–	*	*	*	7
Tippairote (2017; Thailand)	*	*	*	*	–	*	*	*	7
Arnold (1990; USA)	*	*	*	*	–	*	*	*	7
Shin (2014; South Korea)	*	*	–	*	**	*	*	*	8
Tabatadze (2018; Georgia)	*	*	–	*	–	*	*	*	6

NOS New-castle Ottawa Scale.