Table 4. Assessment of both prospective and retrospective cohorts using the Newcastle–Ottawa Scale for cohort studies.

Study	Selection				Comparability	Exposure			Total	Interpretation
	Q1	Q2	Q3	Q4	Q5	Q6	Q7	Q8
Erbay et al [39]	*	*	*	*	**	*	*	*	9	High quality
Gacci et al [46]	*	*	*	*	**	*	*	*	9	High quality
Machado et al [23]	*	*	*	*	*	*	*	*	8	High quality
Li et al [28]	*	*	*	*	*	*	*	-	7	High quality
Best et al [24]	*	*	*	*	**	*	-	-	7	High quality
Burke et al [25]	*	*	*	*	**	*	*	*	9	High quality
Rawlings et al [26]	*	*	*	*	**	*	*	*	9	High quality
Li et al [29]	*	*	*	*	**	*	*	*	9	High quality
Holtmann et al [49]	*	*	*	*	**	*	*	*	9	High quality
Guo et al [31]	*	*	*	*	**	*	*	*	9	High quality
Chen et al [34]	*	*	*	*	**	*	*	*	9	High quality
Ma et al [35]	*	*	*	*	**	*	*	*	9	High quality
Ma et al [36]	*	*	*	*	*	*	*	*	8	High quality
Alkhatatbeh et al [42]	*	*	*	*	**	*	*	*	9	High quality
Ediz et al [43]	*	*	*	*	**	*	*	*	9	High quality
Kayaaslan et al [44]	*	-	*	*	**	*	*	*	8	High quality
Pavone et al [52]	*	-	*	*	*	*	*	*	7	High quality
Song et al [37]	*	-	*	*	*	*	*	*	7	High quality
Quan et al [38]	*	-	*	*	*	*	*	*	7	High quality

-: not available.