Table 3.

Assessment of study quality

	[5]	[19]	[20]	[13]	[16]	[9]	[17]	[18]	[21]	[24]	[22]	[23]	[15]	[14]
Power calculations performed	n	P	n	n	n	n	n	y	y	y	n	n	n	n
Was study adequately powered	y	n	y	y	y	y	y	y	u	y	y	y	y	y
Baseline characteristics of subjects reported	P	n	P	y	P	y	P	n	P	y	n	y	y	n
Subjects inclusion and exclusion criteria specified (or in original survey)	y	P	y	y	y	y	y	y	y	y	y	y	y	y
Exposure ascertained with reliable method	y	y	y	y	y	y	y	y	y	n/a	y	y	y	y
Information on the distribution of exposure(s)	y	y	P	y	y	y	y	y	y	n/a	P	y	n	y
Definition of outcome explicit	y	y	y	y	y	y	y	y	y	y	y	y	y	y
Outcome reliably assessed and validated	y	y	y	n	y	y	y	y	y	y	y	y	y	y
Information on background dietary habits provided	y	y	y	y	y	P	y	n	n	n	y	y	y	y
Information on physical activity provided	n	n	y	n	n	y	n	y	y	y	n	y	y	n
Information on smoking/alcohol drinking provided	n	n	n	n	n	n	n	n	n	n	n	n	n	n
Dose-response assessed	y	y	n	y	y	y	y	y	n	y	n	y	n	n
Adequate adjustment for the effects of confounding variables	n	n	P	n	n	P	P	P	P	P	n	y	y	y
Statistical methods adequately described	y	y	y	y	y	y	y	y	y	y	y	y	y	y
Outcome assessors blinded to exposure status	n/a	n/a	n/a	n/a	n/a	y	n/a	n/a	n/a	P	n/a	y	n/a	n/a
Appropriate duration of follow-up for outcome to occur	n/a	n/a	n/a	n/a	n/a	y	n/a	n/a	n/a	P	n/a	y	n/a	n/a
Information on loss to follow-up provided	n/a	n/a	n/a	n/a	n/a	P	n/a	n/a	n/a	P	n/a	P	n/a	n/a
Design includes control group	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	y	n/a	n/a	n/a	n/a
Control and intervention group(s) comparable at baseline for relevant risk factors/outcome variables	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	y	n/a	n/a	n/a	n/a
Blinding of subjects	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n	n/a	n/a	n/a	n/a
Compliance of subjects with the intervention reported	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	P	n/a	n/a	n/a	n/a
Analyses include an intention to treat analysis	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n	n/a	n/a	n/a	n/a
Maximum score cross-sectional study = 14	9.5	8	9.5	9	9.5		10	10.5	9		7.5		10	9
Maximum score prospective study = 17						13.5						14.5
Maximum score intervention study = 20										13.5