TABLE 2.

NOS scores of included studies.

First author, Year	Selection				Comparability	Outcomes			Scores
	Representativeness of exposed cohort	Selection of non-exposed cohort	Ascertainment of exposure	Demonstration that outcomes of interest was not present at start of study	Comparability of cohorts on the basis of the design or analysis	Assessment of outcomes	Was follow-up long enough for outcomes to occur	Adequacy of follow-up of cohorts
Hu Xin et al. (2020)	☆	☆	—	☆	☆☆	—	☆	☆	7
Lee et al. (2019)	☆	☆	—	☆	☆	☆	☆	☆	7
Tsou et al. (2019)	☆	☆	☆	☆	☆	☆	☆	☆	8
Alcusky et al. (2019)	☆	☆	☆	☆	☆	—	☆	☆	7
Quimby et al. (2018)	☆	☆	☆	☆	☆	☆	—	—	6
Stokes et al. (2018)	☆	☆	☆	☆	☆☆	☆	—	☆	8
Ogunsakin et al. (2018)	☆	☆	☆	☆	☆	—	☆	☆	7
Chang et al. (2017)	☆	☆	—	☆	☆☆	☆	—	☆	7
Spratt et al. (2016)	☆	☆	—	☆	☆	—	☆	☆	6
Kwon et al. (2015)	☆	☆	—	☆	☆☆	☆	☆	☆	8
Sandulache et al. (2014)	☆	☆	—	☆	☆	☆	☆	☆	8