Table 3.

Newcastle-Ottawa Scale for included studies

First author, year	Selection				Comparability	Outcome			Total score
	Representativeness of the cohort	Selection of the non-exposed cohort	Ascertainment of exposure	Outcome of interest not present at start of the study	Of cohorts based on design or analysis (max: ++)	Assessment of outcome	Follow-up, long enough	Adequacy of follow-up of cohorts
Aurore et al,16 2011	+	+	+	+	−	+	+	+	7
Bougouin et al,29 2014	+	+	+	+	++	+	+	+	9
Bro-Jeppesen, et al,17 2012	+	+	+	+	−	+	+	−	6
Callaway et al,7 2014	+	+	+	+	++	+	+	+	9
Casella et al,28 2015	−	−	+	+	+	+	+	−	6
Dankiewicz et al,18 2015	−	+	+	+	++	+	+	+	8
Geri et al,19 2015	+	+	+	+	−	+	+	+	7
Hollenbeck et al,20 2014	−	+	+	+	+	+	+	+	7
Kleissner et al,21 2015	−	+	+	+	−	+	+	+	6
Mooney et al,5 2011	+	+	+	+	−	+	+	+	7
Nanjayya and Nayyar 2012	−	+	+	+	−	+	+	+	6
Nielsen et al,23 2009	−	+	+	+	−	+	+	+	6
Strote et al,24 2012	−	+	+	+	−	+	+	−	5
Tømte et al,25 2011	+	−	+	+	−	+	+	+	6
Vyas et al,6 2014	+	+	+	+	++	+	+	+	9
Weiser et al,26 2013	−	+	+	+	+	+	+	−	6
Zanuttini et al,27 2012	+	+	+	+	−	+	+	+	7