Table 2. Quality assessment of case-control studies included in the meta-analysis, based on the Newcastle-Ottawa Scale.
| Study ID | Selection |
Comparability |
Exposure |
Total score | |||||
| Case definition Adequate (maximum: ★) | Representativeness of cases (maximum: ★) | Selection of controls (maximum: ★) | Definition of controls(maximum: ★) | Comparability of cases and controls based on design or analysisDesign or Analysis (maximum: ★★)a | Ascertainment of exposure (maximum: ★) | Same method of ascertainment for cases and controls (maximum: ★) | Non-response rate (maximum: ★) | ||
| Cho, et al. [28] | ★ | ★ | — | ★ | ★ for age | ★ | ★ | ★ | 7 |
| Barcelo, et al. [23] | ★ | — | — | ★ | ★★ | ★ | ★ | ★ | 7 |
| Di Murro, et al. [29] | ★ | ★ | — | ★ | ★★ | ★ | ★ | ★ | 8 |
| Svatikova, et al. [30] | ★ | — | — | ★ | ★★ | ★ | ★ | ★ | 7 |
| Ishikawa[36] | ★ | ★ | — | ★ | — | ★ | ★ | ★ | 6 |
| Gjorup[31] | ★ | ★ | ★ | ★ | ★ for age | ★ | ★ | ★ | 8 |
| Takahashi[39] | ★ | — | — | ★ | ★★ | ★ | ★ | — | 6 |
| Yao[38] | ★ | — | — | ★ | ★★ | ★ | ★ | — | 6 |
| Moller[32] | ★ | — | — | ★ | ★ for age | ★ | ★ | ★ | 6 |
| Hu[33] | ★ | — | — | — | — | ★ | — | — | 2 |
| Xiao[34] | ★ | — | — | ★ | ★★ | ★ | ★ | — | 6 |
| Maillard[35] | ★ | — | — | ★ | ★★ | ★ | ★ | — | 6 |
aStudies could receive 2-4 ★ for each item, except for “Comparability of cases and controls”, for which one ★ was awarded if the study controlled for age as the most important factor and another ★ if it controlled for BMI as an additional factor. BMI: body mass index.