Table 4.

New Castle Ottawa Scale for Risk of Bias.

Study	Selection				Comparability		Outcome			Overall
	Represent activeness of the exposed cohort	Selection of the non exposed cohort	Ascertainment of exposure	Outcome not present at start	Age factor	Other factor	Assessment of outcome	Adequate follow-up length	Adequacy of follow up
Tatebe et al. (2021)	＊	＊	＊		＊	＊	＊	＊		7
Nakamura et al. (2020)	＊	＊	＊	＊	＊	＊	＊	＊	＊	9
Osanai et al. (2020)	＊	＊	＊	＊	＊	＊	＊	＊	＊	9
Ito et al. (2018)	＊	＊	＊	＊	＊	＊	＊	＊	＊	9
Momosaki et al. (2015)	＊	＊	＊	＊	＊	＊	＊	＊	＊	9
Iwamoto et al. (2014)	＊	＊	＊		＊	＊	＊	＊	＊	8