Table 3.
Risk of bias for primary studies incorporating quantitative research methodologies.
| Study author | Clearly stated research question? | Clearly defined study population? | Participation rate at least 50%? | Subjects recruited from similar populations? | Sample size justification? | Exposure of interest measured prior to outcome? | Timeframe sufficient between exposure and outcome? | Different levels of exposure measured? | Exposure(s) measures clearly defined? | Exposure(s) exposed more than once? | Outcome measures clearly defined? | Outcome assessors blinded to the exposure status? | Loss to follow-up less than 20% | Key confounders measured and adjusted for? | Overall risk of bias |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Batista Ferrer H, et al. [23], [24] | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | NA | ✗ | ✗ | ✗ | NA | NA | ✗ | High |
| Brabin L, et al. [31] | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✓ | ✗ | ✗ | ✗ | NA | NA | ✗ | High |
| Braun R. [32] | ✓ | ✗ | NR | NR | ✗ | ✗ | ✗ | NA | ✗ | ✗ | ✗ | NA | NA | NR | High |
| Carolan K, et al. [33] | ✓ | ✓ | NR | ✓ | ✗ | ✗ | ✗ | NA | ✗ | ✗ | ✗ | NA | NA | ✗ | High |
| Ford C, et al. [34], [35] | ✓ | ✓ | ✗ | ✓ | ✗ | ✗ | ✗ | NA | ✗ | ✗ | ✗ | NA | NA | ✗ | High |
| Kennedy A, et al. [36] | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | NA | ✗ | ✗ | ✗ | NA | NA | ✗ | High |
| Pyrzanowski J, et al. [37] | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | NA | ✗ | ✗ | ✗ | NA | NA | ✗ | High |
| Rand C, et al. [38] | ✓ | ✓ | NR | ✓ | ✗ | ✗ | ✗ | NA | ✗ | ✗ | ✗ | NA | NA | ✗ | High |
| Rylance G, et al. [39] | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | NA | ✗ | ✗ | ✗ | NA | NA | ✗ | High |
| Shah P, et al. [40] | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | NA | ✗ | ✗ | ✗ | NA | NA | ✗ | High |
| Wilson S, et al. [41] | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | NA | ✗ | ✗ | ✗ | NA | NA | ✗ | High |
NR: Not reported; NA: Not applicable