Table 2.
Methodologic quality of the included studies
| Study | Study design | Adequate selection of cases and controls | Adequate assessment of exposure | Adequate assessment of outcome | Adequate control for confounding | Overall score* |
|---|---|---|---|---|---|---|
| Meuller et al.17 | Case–control | Characteristics given: yes Same population: yes Same period: yes |
Described: yes | Described: yes Accurate: yes |
Distribution given: yes Adjustment: yes |
22 |
| Fukuda et al.24 | Case–control | Characteristics given: yes Same population: yes Same period: yes |
Described: yes | Described: yes Accurate: yes |
Distribution given: yes Adjustment: yes |
21 |
| Russell et al.30 | Case–control | Characteristics given: yes Same population: yes Same period: yes |
Described: yes | Described: yes Accurate: yes |
Distribution given: yes Adjustment: yes |
23 |
| Shealy et al.23 | Case–control | Characteristics given: no Same population: yes Same period: yes |
Described: no | Described: yes Accurate: yes |
Distribution given: no Adjustment: no |
10 |
| Sulheim et al.15 | Case–control | Characteristics given: yes Same population: yes Same period: yes |
Described: yes | Described: yes Accurate: yes |
Distribution given: yes Adjustment: yes |
21 |
| Ekeland et al.18 | Case–control | Characteristics given: yes Same population: yes Same period: yes |
Described: yes | Described: yes Accurate: yes |
Distribution given: yes Adjustment: yes |
19 |
| Hagel et al.16 | Case–control and case-crossover | Characteristics given: yes Same population: yes Same period: yes |
Described: yes | Described: yes Accurate: yes |
Distribution given: yes Adjustment: yes |
22 |
| Johnson et al.20 | Case–control | Characteristics given: yes Same population: yes Same period: yes |
Described: yes | Described: yes Accurate: yes |
Distribution given: no Adjustment: no |
12 |
| Macnab et al.21 | Case–control | Characteristics given: yes Same population: yes Same period: yes |
Described: yes | Described: yes Accurate: yes |
Distribution given: no Adjustment: yes |
19 |
| Ekeland et al.19 | Case–control | Characteristics given: yes Same population: yes Same period: yes |
Described: yes | Described: yes Accurate: yes |
Distribution given: yes Adjustment: yes |
19 |
| Machold et al.2 | Cohort | Characteristics given: yes Same population: yes Same period: yes |
Described: no | Described: yes Accurate: yes |
Distribution given: no Adjustment: no |
15 |
| Sandegard et al.22 | Case–control | Characteristics given: no Same population: yes Same period: yes |
Described: no | Described: no Accurate: yes |
Distribution given: no Adjustment: no |
9 |
*
Overall scores for methodologic quality were determined with use of the Downs and Black checklist (maximum score 28).28