Table 2.

Results of quality assessment using the Newcastle-Ottawa Scale for cohort studies

Ref.	Selection				Comparability	Outcome			Scores
	Representativeness of exposure	Selection of the non-exposure	Ascertainment of exposure	Demonstration that outcome was not present at start	Cohorts on the basis of the design or analysis	Assessment	Long follow-up for outcomes to occur	Adequacy of follow-up
Abnet et al[28], 2005	★	★	★	★	★★	☆	★	★	8
Abnet et al[27], 2001	☆	★	★	★	★★	★	★	★	8
Hiraki et al[19], 2008	★	★	★	★	★★	★	☆	☆	7
Hujoel et al[20], 2003	★	★	★	★	★★	★	☆	☆	7
Kim et al[21], 2022	★	★	★	★	★★	★	★	★	9
Michaud et al[29], 2008	★	★	★	★	★★	★	★	★	9
Ndegwa et al[30], 2018	☆	☆	★	★	★★	★	★	★	7
Watabe et al[32], 1998	☆	★	★	★	★★	★	☆	☆	6
Yano et al[33], 2021	★	★	★	★	★★	★	★	★	9