Table 3. Quality assessment scale score for case-control studies included in the meta-analysis¹.

First author, year of publication (reference)	Adequate definition of cases	Representativeness of cases	Selection of control subjects	Definition of control subjects	Control for important factor or additional factor2	Exposure assessment	Same method of ascertainment for all subjects	Nonresponse rate3	Data analysis that used an energy-adjusted residual or nutrient-density model	Total quality scores
Bosetti,2005 [70]	☆	☆	-	☆	☆☆	-	☆	☆	☆	8
Fink,2007 [71]	☆	☆	☆	-	☆☆	-	☆	-	☆	7
Peterson,2003 [72]	☆	☆	-	-	☆☆	-	☆	-	☆	6
Sanchez,2009 [73]	☆	☆	-	☆	☆☆	-	☆	☆	☆	8
Kyle,2010 [76]	☆	☆	☆	-	☆☆	-	☆	☆	☆	8
Rossi,2006 [78]	☆	☆	-	☆	☆☆	-	☆	☆	☆	8
Theodoratou,2007 [79]	☆	☆	☆	-	☆☆	-	☆	-	☆	7
Zamora-Ros,2013 b [80]	☆	☆	-	☆	☆☆	-	☆	☆	☆	8
Bobe,2009 [81]	☆	☆	☆	☆	☆☆	-	☆	☆	☆	9
Petrick,2015 [82]	☆	☆	☆	-	☆☆	-	☆	-	☆	7
Rossi,2007 a [83]	☆	☆	-	☆	☆☆	-	☆	☆	☆	8
Lagiou,2004 a [85]	☆	☆	-	-	☆☆	-	☆	-	☆	6
Rossi,2010 b [86]	☆	☆	-	☆	☆	-	☆	☆	☆	7
Woo,2014 [87]	☆	☆	-	☆	☆☆	-	☆	-	☆	7
Rossi,2007 b [89]	☆	☆	-	☆	☆☆	-	☆	☆	☆	8
Garavello,2007 [90]	☆	☆	-	☆	☆☆	-	☆	☆	☆	8
Lagiou,2008 [91]	-	☆	-	☆	☆	-	☆	☆	☆	6
Christensen,2012 [93]	☆	☆	☆	-	☆☆	-	☆	-	☆	7
Cui,2008 [37]	☆	☆	☆	☆	☆☆	-	☆	-	☆	8
Lagiou,2004 b [95]	☆	☆	-	-	☆☆	-	☆	-	☆	6

¹A study could be awarded a maximum of one star for each item, while two stars for the item Control for important factor or additional factor.

²A maximum of two stars could be awarded for this item. Studies similar to others in terms of patient characteristics (age, sex, BMI) received one star, whereas studies that controlled for other important confounders such as smoking and drinking received an additional star.

³One star was awarded if there was no significant difference in the response rate between control and cases by chi-square test (P> 0.05).