Table 2.

Quality assessment attributes for each study assessed using the Quality Criteria Checklist (QCC)

	Criteria scores
Study	Clear research question	Participant selection free from bias	Comparable study groups	Participant withdrawals or response rate described	Use of blinding	Description of intervention protocol and/or data collection procedures	Outcomes clearly defined	Appropriate statistical analysis	Conclusions supported by results	Unlikely funding bias	Overall quality rating*
Caraher et al. (2013)( 44 )	+	+	+	+	−	+	+	+	+	NR	+
Laska et al. (2012)( 9 )	+	+	N/A	+	N/A	+	+	+	+	+	+
Leal et al. (2011)( 5 )	+	+	N/A	+	N/A	+	+	+	+	+	+
Venter and Winterbach (2010)( 35 )	+	+	N/A	+	N/A	+	+	+	+	+	+
Tsartsali et al. (2009)( 36 )	+	+	N/A	+	N/A	+	+	+	+	+	+
Mirmiran et al. (2007)( 37 )	+	−	N/A	−	N/A	+	+	+	+	NR	Ø
Larson et al. (2006)( 38 )	+	+	N/A	−	N/A	+	+	+	+	+	+
Huang et al. (2004)( 39 )	+	−	N/A	−	N/A	−	+	+	+	NR	−
Pirouznia (2001)( 40 )	+	+	N/A	−	N/A	+	+	+	+	NR	+
Chapman et al. (1997)( 45 )	+	+	+	−	−	+	+	+	+	NR	+
Gracey et al. (1996)( 41 )	+	+	N/A	−	N/A	+	+	+	+	+	+
Osler and Hansen (1993)( 42 )	+	+	N/A	+	N/A	+	+	+	+	+	+
Trexler and Sargent (1993)( 43 )	+	+	N/A	−	N/A	+	+	+	+	+	+

N/A, not applicable (due to cross-sectional design of study); NR, not reported.

*+, positive overall score: this overall score is given if criteria 2, 3, 6 and 7 of the QCC and one additional criterion have received a positive score. Ø, neutral overall score: this score is given if more criteria are met than for a negative overall score but an overall positive score is not reached. −, negative overall score: this score is given if six or more QCC criteria are not met.