Table 2.
Methodological quality assessment by the Newcastle-Ottawa scale
| Studies | Selection | Comparability | Exposure | Total quality score | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| The case definition is adequate with independent validation | Represent-ativeness of cases |
ommunity controls | Controls with no history of disease | Cases and controls with comparable education | Cases and controls with comparable age | Ascertainment of outcome | Same method of ascertainment for cases and controls | Similar non response rate for both groups |
||
| Wang et al (2010)25 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 8 |
| Lui et al (2011)24 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 7 |
| Zhou et al (2014)26 | 1 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 7 |
| Saleem et al (2018)27 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 6 |