Table 2.

Methodological quality evaluation

Included studies		Representativeness of exposed cohort	Selection of non-exposed cohort	Ascertainment of exposure	Study design	Outcome
Authors, years						Assessment of outcome	Length of follow-up
Li et al. [7]	2020	●				●●●	●
Kim et al. [18]	2018	●				●●●
Yang et al. [24]	2018	●	●			●●●	●
Mc Grath et al. [27]	2016	●		●	●	●●
Li et al. [22]	2016	●	●	●	●	●●●	●
Madhavan et al. [26]	2016	●		●	●	●●●
Telfeian et al. [28]	2015	●		●		●●
Ahn et al. [19]	2014	●		●	●	●●●	●
Knight et al. [21]	2014	●	●			●●●	●
Yeung et al. [8]	2014	●				●●●	●
Lewandrowski et al. [17]	2014	●	●			●●	●
Jasper et al. [6]	2013	●	●			●●
Knight et al. [5]	2003	●		●	●	●●●	●
Ahn et al. [4]	2003	●		●		●