Table 2.

Newcastle–Ottawa Scale scores for (a) cohort studies and (b) case–control studies

A
	Selection				Comparability	Outcome
First author, year	Representation of the exposed cohort	Selection of the non-exposed cohort	Ascertainment of exposure	Outcome of interest was not present at the start of study	Comparability of cohorts on the basis of the design or analysis	Assessment of outcome	Was follow-up long enough for outcomes to occur	Adequacy of follow up of cohorts	Total
Wang, (2021)	✶	✶	✶	✶	✶	✶	✶	✶	8
Hsieh, (2020)	✶	✶	✶	✶	✶	✶	✶	✶	8
Kim, (2020)	✶	✶	✶		✶✶	✶	✶	✶	8
Bunch, (2020)	✶	✶	✶		✶✶	✶	✶	✶	8
Bunch, (2011)	✶	✶	✶		✶✶	✶	✶	✶	8
Hyogo, (2019)	✶	✶	✶		✶✶	✶	✶	✶	8
B
	Selection				Comparability	Exposure
First author, year	Case definition	Representativeness of the cases	Selection of controls	Definition of controls	Comparability of cases and controls on the basis of the design	Ascertainment of exposure	Same method of ascertainment for cases and controls	Non response rate	Total
Zhang (2021)	✶	✶	✶	✶			✶	✶	6
Jin (2019)	✶	✶	✶	✶	✶✶	✶	✶	✶	9
Tischer (2019)	✶	✶	✶	✶	✶	✶	✶	✶	8
Medi (2013)	✶	✶	✶	✶			✶	✶	6