TABLE A1.

Risk of bias assessment ^a of the studies with a cross‐sectional design

Author, year	Research question clear	Clearly defined study population	Participation rate >50%	Participants from same population/time and eligibility criteria uniformly applied	Sample size justification	Exposure assessed prior to outcome	Timeframe sufficient to detect exposure and outcome	Different levels of exposure assessed	Exposure measure clearly defined, valid, reliable, applied consistently	Exposure measure assessed more than once	Outcome measures clearly defined, valid, reliable and applied consistently	Outcome assessors blinded to exposure	Key confounders measured and adjusted for
Sinha et al. (2018)	Yes	Yes	No	Yes	No	No	No	No	No	No	No	?	Yes
Lawson et al. (2017)	Yes	No	Yes	Yes	No	No	No	Yes	Yes	No	Yes	?	Yes
Bailey et al. (2016)	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	No	Yes	?	Yes
Bates et al. (2012)	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	?	Yes

^a Quality assessment was performed using the Quality assessment tool for observational, cohort and cross‐sectional studies of the National Institute of Health. Questions are answered with yes or no. When it was unclear, a question mark was reported.