Table 5.

Newcastle–Ottawa Quality Assessment Scale for cohort studies

Studies	Selection				Comparability	Outcome			Total score
	Representativeness of the exposed cohort	Selection of non-exposed cohort	Ascertainment of exposure	Demonstration that outcome of interest was not present at start of study	Comparability of cohorts on the basis of the design analysis	Assessment of outcome	Was follow up long enough for outcomes to occur	Adequacy of follow up of cohorts
Schoolcraft (2010)		*	*	*	**	*	*	*	8/9
Forman (2012)		*	*	*		*	*	*	6/9
Schoolcraft (2013)		*	*	*	*	*	*	*	7/9
Lee (2015)		*	*	*	**	*	*	*	8/9
Kang (2016)		*	*	*		*	*	*	6/7
Whitney (2016)		*	*	*	*	*	*	*	7/9
Coates (2017)		*	*	*	*	*	*	*	7/9
Liss (2018)		*	*	*	**	*	*	*	8/9
Lee (2019)		*	*	*		*	*	*	6/9
Sato (2019)		*	*	*	**	*	*	*	8/9