Table 3.

Risk of bias quality assessment

	Study type	Selection				Comparability		Exposure/Outcome			Sub total assessment			Conclusion	Total
		1	2	3	4	1a	1b	1	2	3	S	C	E
Mazurkiewicz et al. [17]	cross-sectional	*	no	*	**	*	*	*	*	*	good	good	good	GOOD	7
Kim et al. [18]	cohort	*	*	*	no	*	*	*	*	no	good	good	good	GOOD	7
Bai et al. [19]	cohort	*	*	*	no	*	*	*	no	no	good	good	fair	GOOD	6
Fernandez-de-las-Peñas et al. [20]	cohort	*	*	no	no	*	*	*	no	no	fair	good	fair	FAIR	5
Michelutti et al. [21]	cross-sectional	*	*	*	*	*	*	*	*	*	good	good	good	GOOD	8
Fjelltveit et al. [22]	case-control-	*	*	*	no	*	*	*	*	no	good	good	good	GOOD	7
Weinstock et al. [23]	cross-sectional	*	no	no	*	*	*	*	no	*	fair	good	good	FAIR	5
Aparisi et al. [24]	case-control	*	*	*	no	*	*	*	*	no	good	good	good	GOOD	7
Sykes et al. [25]	cohort	*	*	*	no	*	*	*	*	no	good	good	good	GOOD	7
Pelà et al. [26]	cohort	*	no	*	*	*	no	*	*	*	good	fair	good	GOOD	7
Ganesh et al. [9]	cohort	no	*	*	*	*	*	*	*	*	good	good	good	GOOD	8
Gebhard et al. [27]	cohort	*	*	*	*	*	*	*	*	*	good	good	good	GOOD	9