Table 2.

Risk of bias assessment.

	Klang et al.	Hamer et al.	Simonnet et al.	Hu et al.	Kalligeros et al.	McMichael et al.	Richardson et al.	Cai et al.	Zheng et al.	Deng et al.	Petrilli et al.	Lighter et al.
Are the study group at risk of not representing their source populations in a manner that might introduce selection bias?	Unclear	High	Unclear	Low	Low	Unclear	Low	Low	Unclear	Low	Low	Low
Was knowledge of the group assignments adequately prevented (i.e., blinded or masked) during the study, potentially leading to the subjective measurement of either exposure or outcome?	Unclear	Unclear	Low	Low	Low	Low	Low	Low	Low	Low	Unclear	Low
Were exposure assessment methods lacking accuracy?	Low	Low	Low	Low	Low	Low	Low	Unclear	Low	Low	Low	Low
Were outcome assessment methods lacking accuracy?	Low	Low	Low	Low	Low	Low	Low	Unclear	Low	Unclear	Low	Low
Was potential confounding inadequately incorporated?	Unclear	Low	Low	Unclear	Low	High	Unclear	Low	Low	Unclear	Unclear	Unclear
Were incomplete outcome data inadequately addressed?	Low	Low	Low	Unclear	Low	Low	Low	Low	Low	Unclear	Low	Low
Does the study report appear to have selective outcome reporting	Low	Low	Low	Low	Low	Low	Low	Low	Low	Low	Low	Low
Did the study receive any support from a company, study author, or other entity having a financial interest in any of the exposures studied?	Low	Low	Low	Low	Low	Unclear	Low	Low	Low	Low	Low	Low
Did the study appear to have problems that could put it at risk of bias?	Low	Low	Low	Low	Low	Low	Low	Low	Low	Low	Low	Low
Total score (Extra 2 points for peer-reviewed article)	17	17	19	18	20	16	19	18	19	17	16	17