Table 2.

Quality assessment.

Author and year	Q1	Q2	Q3	Q4	Q5	Q6	Q7	Q8	Q9	Q10	Q11	Q12	Q13	Q14	# of items free of bias	% of items free of bias	Qualitative rating
Observational cohort a
Buigues et al. 2020	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	CD	Yes	Yes	12	86	Good
Dalmasso et al. 2018	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	No	CD	Yes	Yes	11	79	Good
Falandry et al. 2015	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	No	Yes	CD	Yes	Yes	11	79	Good
Gilmore et al. 2020	Yes	Yes	NR	Yes	No	Yes	Yes	Yes	Yes	No	No	CD	Yes	Yes	9	64	Fair
Gilmore et al. 2021	Yes	Yes	NR	Yes	No	Yes	Yes	Yes	Yes	Yes	No	CD	Yes	Yes	10	71	Good
Harneshaug et al. 2019	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	No	No	CD	Yes	Yes	10	71	Good
Ronning et al. 2010	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	No	Yes	CD	Yes	No	10	71	Good
Cross-sectional a
Brouwers et al. 2015	Yes	Yes	NR	Yes	No	No*	No*	Yes	Yes	No*	No	CD	No*	No	5	50	Fair
Corona et al. 2014	Yes	Yes	Yes	Yes	No	No*	No*	Yes	Yes	No*	No	CD	No*	No	6	60	Fair
Hatse et al. 2014	Yes	Yes	Yes	Yes	No	No*	No*	Yes	Yes	No*	No	CD	No*	No	6	60	Fair
Lealdini et al. 2015	Yes	Yes	NR	Yes	No	No*	No*	Yes	Yes	No*	Yes	CD	No*	No	6	60	Fair
Navarro-Martinez et al. 2019	Yes	Yes	NR	No	No	No*	No*	Yes	Yes	No*	Yes	CD	No*	CD	5	50	Fair
Nishijima et al. 2017	Yes	Yes	NR	Yes	No	No*	No*	Yes	Yes	No*	Yes	CD	No*	Yes	7	70	Fair
Case–control b
	Q1	Q2	Q3	Q4	Q5	Q6	Q7	Q8	Q9	Q10	Q11	Q12	# of items free of bias	% of items free of bias	Qualitative rating
Bylow et al. 2011	Yes	Yes	No	Yes	Yes	Yes	CD	CD	Yes	Yes	CD	No	7	58	Fair

*Questions that were not applicable to cross-sectional design studies were not counted toward overall score.

^aCohort and cross-sectional studies were evaluated using NIH quality assessment tool for observational cohort and cross-sectional.

^bCase-control study was evaluated using the quality assessment tool for case-control studies.

^cCancer group had multivariate analyses but not the control group.