Table 2. Quality assessment of studies using Newcastle-Ottawa scale for case-control studies.

Study ID	Selection				Comparability	Exposure			Total (max = 9⋆)
	Case definition (⋆)	Representativeness of the cases (⋆)	Selection of Controls (⋆)	Definition of Controls (⋆)	(⋆⋆)	Ascertainment of exposure (⋆)	Same method of ascertainment for cases and controls (⋆)	Non-Response rate (⋆)
Alshuft et al. (2016)	⋆	–	–	⋆	–	⋆	⋆	⋆	5
Baliki et al. (2011)	–	–	–	–	⋆⋆	⋆	⋆	–	4
Baliki et al. (2014)	–	–	–	–	–	⋆	⋆	⋆	3
Barroso et al. (2020)	⋆	–	⋆	⋆	–	⋆	–	⋆	5
Barroso et al. (2020)	⋆	–	⋆	⋆	⋆⋆	⋆	–	–	6
Cheng et al. (2022)	⋆	–	−	⋆	⋆⋆	⋆	–	–	5
Cottam et al. (2016)	⋆	–	–	–	–	⋆	⋆	–	3
Cottam et al. (2018)	⋆	–	–	–	**	⋆	–	–	5
Gao et al. (2022)	⋆	−	⋆	–	–	⋆	–	⋆	4
Guo et al. (2021)	⋆	−	–	⋆	⋆⋆	⋆	–	⋆	6
Kang et al. (2021b)	⋆	–	–	–	⋆⋆	⋆	–	⋆	5
Lan et al. (2020)	⋆	–	⋆	⋆	⋆⋆	⋆	–	⋆	7
Lewis et al. (2018)	–	⋆	–	⋆	⋆⋆	⋆	–	⋆	6
Liao et al. (2018)	⋆	–	–	⋆	⋆⋆	⋆	–	⋆	6
Mao et al. (2016)	⋆	–	⋆	–	–	⋆	–	⋆	4
Ushio et al. (2020)	⋆	–	–	⋆	⋆⋆	⋆	–	⋆	6