Table 3. Quality assessment of longitudinal studies using the Newcastle-Ottawa Scale.

Author and year	Salvago et al., 2022 [12]	Jeong et al., 2021 [14]	Niu et al., 2020 [18]	Labaeka et al., 2018 [20]	Poonual et al., 2016 [22]
Selection
Representativeness of the exposed cohort	*	*	*	*	*
Selection of the nonexposed cohort	*	*	*	*	*
Ascertainment of exposure	*	X	*	*	*
Demonstration that the outcome of interest was not present at the start of the study	*	*	*	*	*
Comparability
Comparability of cohorts on the basis of the design or analysis controlled for confounders	**	*	*	**	*
Outcome
Assessment of outcome	*	*	X	*	*
Was follow-up long enough for outcomes to occur?	*	*	*	*	X
Adequacy of the follow-up of cohorts	*	*	*	*	*
Total score	9	7	7	9	7
Overall grade	Good	Good	Good	Good	Good