Table 2.
Risk of Bias in Individual Studies
| Criteria | Panczak et al. 2017 [25] | Hanratty et al. 2007 [30] | Shugarman et al. 2004 [38] | Tanuseputro et al. 2015 [11] | Cunningham et al. 2011 [24] | Kelley et al. 2015 [26] | Kelley et al. 2013 [28] | Kelley et al. 2011 [29] | Lee et al. 2015 [27] | Fahlman et al. 2006 [31] | McGarry et al. 2005 [32] | Hogan et al. 2001 [33] | Timmer & Kovar 1971 [34] | Chen et al. 2017 [35] | Hanchate et al. 2009 [36] | Keating et al. 2018 [37] | Rolden et al. 2014 [39] | Murthy et al. 2017 [40] | Walsh & Laudicella 2017 [41] | Menec et al. 2004 [42] |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Was the research question or objective in this paper clearly stated? | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y |
| Was the study population clearly specified and defined? | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y |
| Was the participation rate of eligible persons at least 50%? | Y | Y | N | Y | Y | N | Y | Y | Y | Y | Y | N | Y | Y | NR | Y | N | Y | Y | Y |
| Were all the subjects selected from the same or similar populations (including the same time period)? Were inclusion and exclusion criteria for being in the study prespecified and applied uniformly to all participants? | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | NR | Y | Y | Y | Y | Y |
| Did the study examine different levels of the exposure as related to the outcome? (i.e. SES measured as a continuous variable) | Y | Y | Y | Y | Y | N | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y |
| Were the exposure measures (independent variables) clearly defined, valid, reliable, and implemented consistently across all study participants? (i.e. individual/household SES) | N | Y | N | N | Y | Y | Y | Y | Y | N | Y | N | Y | Y | N | Y | N | N | N | N |
| Were the outcome measures (dependent variables) clearly defined, valid, reliable, and implemented consistently across all study participants? | Y | Y | Y | Y | Y | Y | Y | Y | N | Y | N | N | N | Y | Y | Y | Y | Y | Y | Y |
| Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure(s) and outcome(s)? (i.e. adjusted for health status) | N | N | Y | N | Y | N | N | N | Y | Y | N | N | N | Y | Y | Y | N | Y | Y | N |
| Quality of Study | Medium | High | Medium | Medium | High | Medium | High | High | High | High | Medium | Low | Medium | High | Medium | High | Medium | High | High | Medium |
CD cannot be determined; NA Not applicable; NR Not reported