Table 4.

Risk of bias table using the Newcastle Ottawa Quality Assessment Scale for cohort studies

Study	Selection				Comparability	Outcome
	Representativeness of exposed cohort	Selection of non-exposed cohort	Ascertainment of exposure	Outcome of interest was not present at the start of the study	Comparability of cohorts on the basis of design or analysis	Assessment of outcome	Was follow-up long enough for the events to occur?	Adequacy of follow-up cohorts
Al-Qahtani et al. [40]	*	*	*	*		*	*	*
Baxter et al. [41]	*	*	*	*		*	*	*
Beitler et al. [42]			*	*		*	*	*
Bellomo et al. [22]	*	*	*	*	*	*	*	*
Buist et al. [44]	*	*		*	*	*	*
Campello et al. [45]	*		*	*		*	*	*
Dacey et al. [46]	*	*	*	*	*	*
DeVita et al. [47]	*	*	*	*				*
Hayani et al. [48]			*	*		*	*
Jones et al. [50]	*	*	*	*		*	*
Kenward et al. [51]	*	*	*	*	*	*	*
Konrad et al. [14]	*	*	*	*	*	*	*	*
Lim et al. [52]	*	*	*	*		*		*
Santamaria et al. [53]	*	*	*	*	*	*	*	*
Shah et al. [54]	*	*	*	*	*	*	*	*
Simmes et al. [55]			*	*		*
Brilli et al. [56]	*	*	*	*	*	*	*	*
Anwar ul Haque et al. [58]		*		*		*	*
Hunt et al. [59]	*	*	*	*		*	*	*
Kotsakis et al. [60]				*	*		*	*
Sharek et al. [61]	*	*	*	*	*	*	*	*
Tibballs and Kinney [23]	*	*		*		*	*	*
Zenker et al. [62]		*		*		*	*	*