Table 3 Summary of study quality
Randomised controlled trials | Random allocation | Baseline measurement | Reliability of outcome measure | Blinding | Adequacy of follow-up | Protection against contamination |
|---|---|---|---|---|---|---|
Donnelly, et al. 2009 [62] | Completed | Completed | Not clear | Completed | Adequate | Completed |
Foster, et al. 2008 [55] | Completed | Completed | Sufficient | Not blinded | Significant loss to follow-up | Completed |
Controlled before-after studies | Second site control | Baseline measurement | Reliability of outcome measure | Blinding | Adequacy of follow-up | Protection against contamination |
Heelan, et al. 2009 [61] | Sufficient | Completed | Sufficient | Not clear | Significant loss to follow-up | Completed |
Johnson, et al. 2012 [31] | Sufficient | Completed | Sufficient | Not done | Adequate | Completed |
Jordan, et al. 2008 [64] | Sufficient | Not clear | Not clear | Not clear | Significant loss to follow-up | Completed |
Cohort Studies | Representativeness of the cohort/sample | Comparability of cohorts | Ascertainment of exposure | Assessment of outcome | Duration of exposure | Adequacy of exposure |
Baxter, et al. 2009 [53] | Not described | Not indicated | Measured as part of the study | Independent of exposure | Sufficient | No statement |
Chiodera, et al. 2008 [60] | Representative | Did not control for socioeconomic status or ethnicity | Measured as part of the study | Independent of exposure | Sufficient | Sufficient |
Chomitz, et al. 2010 [63] | Somewhat representative | Controlled for ethnicity, socioeconomic status and additional factors | Measured as part of the study | Independent of exposure | Sufficient | Subjects lost to follow-up unlikely to introduce bias |
Datar and Sturm, 2004 [38] | Representative | Controlled for ethnicity, socioeconomic status and additional factors | Measured as part of the study | Independent of exposure | Sufficient | Subjects lost of follow-up may have introduced bias |
Representative | Controlled for ethnicity, socioeconomic status and additional factors | Structured interview | Independent of exposure | Sufficient | Subjects lost to follow-up may have introduced bias | |
Henry, 2006 [50] | Somewhat representative | Did not control for socioeconomic status or ethnicity | Measured as part of the study | Independent of exposure | Sufficient | Sufficient |
Hernandez. Francis and Doyle, 2011 [41] | Representative | Controlled for ethnicity, socioeconomic status and additional factors | Written self report | Independent of exposure | Sufficient | Sufficient |
Hinrichs, 2006 [47] | Representative | Controlled for ethnicity and, socioeconomic status | Measured as part of the study | Independent of exposure | Sufficient | No statement |
Millimet and Tchernis, 2009 [42] | Somewhat representative | Controlled for ethnicity, socioeconomic status and additional factors | Measured as part of the study | Independent of exposure | Sufficient | Subjects lost to follow-up may have introduced bias |
Representative | Controlled for ethnicity, socioeconomic status and additional factors | Measured as part of the study | Independent of exposure | Sufficient | Sufficient | |
Ramirez-Lopez, et al. 2005 [54] | Somewhat representative | Controlled for some factors but not socioeconomic status or ethnicity | Measured as part of the study | No description | Sufficient | Subjects lost to follow-up may have introduced bias |
Cross-sectional Studies | Representativeness of the cohort/sample | Comparability of cohorts | Ascertainment of exposure | Assessment of outcome | Duration of exposure | Adequacy of exposure |
Fox, et al. 2009 [56] | Somewhat representative | Controlled for ethnicity, socioeconomic status and additional factors | Measured as part of the study and structured interviews | Independent of exposure | Sufficient | Sufficient |
Jones, et al. 2003 [34] | Somewhat representative | Controlled for ethnicity and, socioeconomic status | Measured as part of the study | Independent of exposure | Sufficient | Sufficient |
Harrison, et al. 2011 [57] | Somewhat representative | Controlled for socioeconomic status | Measured as part of the study | Independent of exposure | Sufficient | Subjects lost to follow-up may have introduced bias |
Veugelers and Fitzgerald, 2005 [58] | Somewhat representative | Controlled for socioeconomic status and additional factors | Measured as part of the study | Independent of exposure | Sufficient | Sufficient |
Zhu, et al. 2010 [59] | At risk group | Did not control for socioeconomic status or ethnicity | Measured as part of the study | Independent of exposure | Sufficient | Subjects lost of follow-up unlikely to introduce bias |