Table 1. Detailed Newcastle-Ottawa Scale of each included study.

Study	Selection				Comparability		Exposure			NOS
	a	b	c	d	e	f	g	h	i
Hamdi, Al-Hababi & Eid (2014)	*	*	*	*	*		*	*		7
Pan et al. (2019)	*	*	*	*	*		*	*		7
Nassar et al. (2017)	*	*	*	*	*		*			6
Mosaad et al. (2014)	*	*	*	*	*	*	*	*		8
Rivera et al. (2012)	*	*	*	*	*		*	*		7
Al-Taie et al. (2012)	*	*	*	*	*		*	*	*	8
Ademović-Sazdanić & Vojvodić (2019)	*	*	*	*	*		*	*		7
Shao et al. (2018)	*	*	*	*	*		*	*		7
Nassar, Al-Shamahy & Masood (2015)	*	*	*	*	*		*			6
Karahan et al. (2009)	*	*	*	*	*		*	*		7
Noureen et al. (2020)	*	*	*	*	*		*	*		8
Chowdhry, Makroo & Kumar (2016)	*	*	*	*	*		*	*		7
Patel et al. (2013)	*	*	*	*	*		*	*		7
Shang et al. (2016)	*	*	*	*	*		*	*		7
Almogren, Shakoor & Hamam (2012)	*	*	*	*	*		*	*		7
Cao et al. (2014)	*	*	*	*	*		*	*		7
Dai et al. (2015a) & Dai et al. (2015b)	*	*	*	*	*		*			6
Hieu, Ha & Nghi (2019)	*	*	*	*	*		*	*		7
Nassar, Al-Shamahy & Masood (2015)	*	*	*	*	*		*			6
Kodaz, Akdeniz & Cengiz (2017)	*	*	*	*	*		*	*		7
Pérez-Luque et al. (2000)	*	*	*	*	*		*	*	*	8
Shaheen et al. (2013)	*	*	*	*	*		*	*		7
Bhallil et al. (2017)	*	*	*	*	*		*			6
Fejzić et al. (2017)	*	*	*	*	*		*	*		7
De Holanda et al. (2018)	*	*	*	*	*		*	*		7
Rostami et al. (2013)	*	*	*	*	*		*	*		7