Table 3.

Newcastle-Ottawa Scale; all the 11 studies were prospective ones

Authors & year of publication	Selection				Comparability	Outcome			Total score
	a	b	c	d	e	f	g	h
Chaturvedi & 1995	*	*	*	*	**	* *	*	*	10
Cho & 2002	/	*	/	*	**	*	*	*	7
Chung & 2017	*	*	*	*	**	**	*	*	10
Strelitz & 2021	*	*	*	*	**	**	*	*	10
Moazzeni &2021	*	*	*	*	**	*	*	*	9
Casanova & 2020	*	*	*	*	*	*	*	*	8
Strelitz & 2019	*	*	*	*	**	**	*	*	10
Polemiti & 2021	*	*	/	*	**	*	*	*	8
Cui & 2021	*	*	*	*	*	**	*	*	9
Aucott & 2016	*	*	*	*	**	**	*	*	10
Liu & 2020	/	*	/	*	*	**	*	*	7

Notes: a = representativeness of exposed cohort; b = selection of the non-exposed cohort; c = ascertainment of cohort; d = that outcome of interest not present at the start of the study; e = comparability; f = assessment of outcome; g = follow-upped long enough until the outcomes occur; h = adequacy of follow-up of cohort