Table 4.

Risk of bias in cohort studies.

References	Were the two groups similar and recruited from the same population?	Were the exposures measured similarly to assign people to both exposed and unexposed groups?	Was the exposure measured in a valid and reliable way?	Were confounding factors identified?	Were strategies to deal with confounding factors stated?	Were the groups/ participants free of the outcome at the start of the study (or at the moment of exposure)?	Were the outcomes measured in a valid and reliable way?	Was the follow up time reported and sufficient to be long enough for outcomes to occur?	Were strategies to address incomplete follow up utilized?	Was appropriate statistical analysis used?
Orta et al. (40)	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Unclear	Unclear	Yes
Karakurum et al. (42)	Yes	Yes	Yes	Unclear	Unclear	Unclear	Yes	Unclear	Unclear	Yes