Table 2

Risk of bias assessment of all included studies

RQ	Study	Study desing	Q1 inclusion criteria	Q2 study population	Q3 exposure	Q4 objective	Q5 confounding factors	Q6 confounding factors	Q7 outcomes measure	Q8 statistical analysis	Number of ✓	RoB
RQ1	Humby et al15	Retrospective cohort	✓	✓	✓	✓	✕	✕	✓	✓	6/8	Unclear
RQ1	Just et al16	Retrospective cohort	✓	✓	✓	✓	✓	✕	✓	✓	7/8	Unclear
RQ2	Kraan et al17	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	6	High
	Musters et al18	Cross-sectional	✓	✓	✓	✕	✕	✕	✓	✓	5	High
	Triaille et al19	Cross-sectional	✓	✓	✓	✓	✕	✕	✓	✓	6	Unclear
RQ3	Donlin et al20	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	5	High
	Smeets et al21	Cross-sectional	✓	✓	✓	✓	✕	✕	✓	✓	6	Unclear
	Kirkham et al22	Cross-sectional	✓	✓	✓	✓	✕	✕	✓	✓	6	Unclear
	Kennedy et al23	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	5	High
	Boyle et al24	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	5	High
	Humby et al11	Retrospective cohort	✓	✓	✓	✓	✕	✕	✓	✓	6	Unclear
	Musters et al18	Cross-sectional	✓	✓	✓	✕	✕	✕	✓	✓	5	High
	Scire et al25	Cross-sectional	✓	✓	✓	✓	✕	✕	✓	✓	6	Unclear
RQ5	Beaten et al26	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	5	High
	Tak et al27	Cross-sectional	✓	✓	✓	✓	✕	✕	✓	✓	6	Unclear
	Tak et al28	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	5	High
	Ospelt et al29	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	5	High
	Dubikov and Kalinichenko30	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	5	High
	Alivernini et al31	Cross-sectional	✓	✓	✓	✓	✓	✕	✓	✓	7	Unclear
	Alivernini et al32	Cross-sectional	✓	✓	✓	✓	✓	✕	✓	✓	7	Unclear
	Rivellese et al33	Cross-sectional	✓	✓	✓	✓	✓	✕	✓	✓	7	Unclear
	Katrib et al40	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	5	High
	Ostojic et al35	Cross-sectional	✓	✓	✓	✓	✓	✕	✓	✓	7	Unclear
	Guo et al35	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	5	High
	Guo et al36	Cross-sectional	✓	✕	✓	✓	✕	✕	✓	✓	5	High
	Lequerré et al37	Cross-sectional	✓	✓	✓	✓	✓	✕	✓	✓	7	Unclear
	Alivernini et al38	Cross-sectional	✓	✓	✓	✓	✓	✕	✓	✓	7	Unclear

RoB, risk of bias; RQ, research question; Q, question