Table.

e-3. Quality of the observational studies.

Author, Year	Research Question/ Objective Clearly Stated?	Study Population Specified and Defined?	Participation Rate of Eligible Persons >50%?	Subjects from Same/Similar Populations? Inclusion/ Exclusion Criteria Prespecified and Applied Uniformly?	Sample Size Justification, Power Description, Variance and Effect Estimates Provided?	Exposure(s) Measured Prior to the Outcome(s) Measured?	Sufficient Timeframe for Association between Exposure and Outcome to be Seen?	Did the Study Examine Different Levels of the Exposure as Related to the Outcomes?	Exposure Measures Defined, Valid, Reliable and Implemented Consistently?	Exposure(s) Assessed more than Once Over Time?	Were Outcomes Assessed Reliable and Consis- tent?	Were Assessors Blinded to Exposure Status of Parti- cipants?	Was Loss to Follow-up after Baseline <20%?	Key Potential Confounding Variables Measured and Adjusted Statistically for their Impact on Relationship between Exposure(s) and Outcome(s)?	Overall Quality
Dunn & Davis, 1974 [63]	+	-	?	+	-	-	-	-	+	-	-	N/A	N/A	-	POOR
Malec et al., 1982 [64]	+	-	+	+	-	-	-	-	+	-	+	N/A	N/A	-	POOR
Heinemann et al., 1991 [65]	+	-	+	+	-	N/A	+	-	-	+	+	N/A	+	+	POOR
Rothstein et al., 1992 [66]	+	-	?	+	-	-	-	+	+	N/A	+	N/A	N/A	-	POOR
Young et al., 1995 [43]	+	-	-	+	-	-	-	+	+	-	+	N/A	N/A	+	POOR
Kolakowsky-Hayer et al., 2002 [67]	+	+	?	+	-	-	-	+	+	-	+	N/A	N/A	+	FAIR
Warms et al., 2002 [68]	+	+	+	+	-	-	-	-	+	-	+	N/A	N/A	-	POOR
Grotenhermen & Schnelle, 2003 [51]	+	-	?	+	-	-	-	+	+	-	+	N/A	N/A	-	POOR
Gorter, 2005 [52]	+	-	-	+	-	-	-	+	+	-	-	N/A	N/A	-	POOR
Cardenas & Jensens, 2006 [53]	+	+	+	+	-	-	-	+	+	-	-	N/A	N/A	-	POOR
Mahoney et al., 2007 [69]	+	-	+	+	N/A	-	-	-	+	-	+	N/A	N/A	N/A	POOR
Aggarwal et al., 2009 [46]	+	-	+	+	-	-	?	-	+	N/A	-	N/A	N/A	N/A	POOR
Heutink et al., 2011 [70]	+	+	+	+	-	-	-	+	+	-	+	N/A	N/A	-	POOR
Hwang et al., 2012 [48]	+	-	?	+	-	-	-	+	+	-	+	N/A	N/A	+	FAIR
Fekete et al., 2015 [42]	+	+	+	+	-	-	-	+	+	-	+	N/A	N/A	+	FAIR
Shroff, 2015 [54]	+	-	?	+	N/A	-	-	-	+	-	+	N/A	N/A	N/A	POOR
Author, Year	Research Question/ Objective Clearly Stated?	Study Population Specified and Defined?	Participation Rate of Eligible Persons >50%?	Subjects from Same/Similar Populations? Inclusion/ Exclusion Criteria Prespecified and Applied Uniformly?	Sample Size Justification, Power Description, Variance and Effect Estimates Provided?	Exposure(s) Measured Prior to the Outcome(s) Measured?	Sufficient Timeframe for Association between Exposure and Outcome to be Seen?	Did the Study Examine Different Levels of the Exposure as Related to the Outcomes?	Exposure Measures Defined, Valid, Reliable and Implemented Consistently?	Exposure(s) Assessed more than Once Over Time?	Were Outcomes Assessed Reliable and Consis- tent?	Were Assessors Blinded to Exposure Status of Parti- cipants?	Was Loss to Follow-up after Baseline <20%?	Key Potential Confounding Variables Measured and Adjusted Statistically for their Impact on Relationship between Exposure(s) and Outcome(s)?	Overall Quality
Drossel et al., 2016 [45]	+	-	+	+	-	-	-	+	+	-	+	N/A	N/A	-	POOR
Andresen et al., 2017 [44]	+	+	+	+	-	-	-	+	+	-	+	N/A	N/A	+	FAIR
Clark et al., 2017 [47]	+	+	+	+	-	-	-	+	+	-	+	N/A	N/A	+	FAIR
Patel et al., 2017 [71]	+	-	+	+	-	-	?	-	+	N/A	+	N/A	N/A	-	FAIR
Bruce et al., 2018 [50]	+	-	+	+	-	-	-	+	+	-	+	N/A	N/A	N/A	POOR
Hawley et al., 2018 [49]	+	-	?	+	-	-	-	+	+	-	+	N/A	N/A	-	POOR
Bourke et al., 2019 [72]	+	-	?	+	N/A	-	-	-	+	-	+	N/A	N/A	N/A	POOR
Eldridge et al., 2019 [73]	+	-	-	+	-	-	?	-	+	-	+	N/A	N/A	-	POOR
Graupensperger et al., 2019 [74]	+	-	+	+	-	-	?	-	+	-	+	N/A	N/A	+	FAIR
Stillman et al., 2019 [75]	+	-	-	+	-	-	-	+	+	-	+	N/A	N/A	-	POOR

Note: N/A: not applicable, for study designs where the question could not be applied; ?: cannot be determined; +: yes; -: no.