Table 3. Assessment of retrospective cohort studies - Newcastle-Ottawa Scale (NOS)
Reference	Selection	Comparability	Exposure/Outcome	Total NOS-score	Comments
Lopéz-Pelayo et al., 2018	★★★★	-	★★★	7
Gu et al. 2016	★★★★	★★	★	7
De Vos et al., 2015	★★★★	★★	★★★	9
Lin et al., 2015	★★★★	-	★★★	7
Lin et al. 2013,	★★★★	-	★★★	7	CPR only mentioned in laboratory protocol section
Eskild et al., 2013	★★★★	★★	★★★	9