Table 2.

Newcastle–Ottawa quality assessment scale (NOS) for the included studies.

Study	Selection				Comparability of cohorts on the basis of the design or analysis	Outcome			Final score
	Representativeness of the exposed cohort	Selection of the non-exposed cohort	Ascertainment of exposure	Demonstration that outcome of interest was not present at start of study		Assessment of outcome	Was follow-up long enough for outcomes to occur	Adequacy of follow up of cohorts
Zhai et al., 2019	*	*	*	*	*	*	*	*	8
Chen et al., 2022	*	*	*	*	-	*	*	*	7
Zhang et al., 2021	*	*	*	*	*	*	*	*	8
Tan et al., 2020	*	*	*	*	*	*	*	*	8
Xu et al., 2021	*	*	*	*	*	*	*	*	8
Zhai et al., 2021	*	*	*	*	*	*	*	*	8
Nam, 2019	*	*	*	*	*	*	*	*	8