Table 4.

Risk of bias assessment for included cohort studies

	Selection				Comparability		Outcome
Studies	Representativeness of exposed cohorts	Selection of the non-exposed cohort	Ascertainment of exposure	Demonstration that outcome of interest was not present at start of study	Comparability of cohorts on the basis of the design or analysis		Assessment of outcome	Was follow-up long enough for outcome to occur	Adequacy of follow-up of cohorts	Total score (maximum score =9)
					Controls for age	Controls for any additional factor
Ottaviani 2012		*	*	*	*	*	*	*	*	8
Micheroli 2017		*	*	*	*	*	*	*	*	8
Rosas 2017		*	*	*	*	*	*	*	*	8
Al-Osami 2018		*	*	*	*	*	*	*	*	8
Ancuta 2018		*	*	*	*	*	*	*	*	8

Each item is scored between 0 and 2, represented by *. Empty cells represent a score of 0.