Table 2. Newcastle-Ottawa Quality Assessment Scale of included studies.
| Study | Selection | Comparability | Outcome | Score | |||||
|---|---|---|---|---|---|---|---|---|---|
| Representativeness of Exposed Cohort1 | Selection of Nonexposed Group2 | Ascertainment of Exposure3 | Outcome of Interest4 | Comparability of Cohorts5 | Assessment of Outcome6 | Length of Follow-up7 | Adequacy of Follow-up8 | ||
| Chen[14] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
| Zhang[15] | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 0 | 7 |
| Yang [16] | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 7 |
| Zheng [17] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Qi [18] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Liu [19] | 1 | 1 | 1 | 1 | 2 | 1 | 0 | 1 | 8 |
| Wang[20] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Yan[21] | 1 | 1 | 1 | 1 | 2 | 1 | 0 | 0 | 7 |
| Feng[22] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Ouyang[23] | 1 | 1 | 1 | 1 | 2 | 1 | 0 | 1 | 8 |
| Rong [24] | 1 | 1 | 1 | 1 | 2 | 1 | 0 | 1 | 8 |
| Ma[25] | 1 | 1 | 1 | 1 | 2 | 1 | 0 | 1 | 8 |
Score was achieved for each item if.
1.
The exposed cohort truly or somewhat represented the average in the community.
2.
The non-exposed cohort was drawn from the same community as the exposed cohort.
3.
Ascertainment of exposure was secure record or structured interview.
4.
Outcome of interest was not present at start of study.
5.
Study controls for the most important factor.
6.
Assessment of outcome was from independent blind assessment or record linkage.
7.
Follow-up was long enough for outcomes to occur.
8.
No subject lost to follow-up or subjects lost to follow-up unlikely to introduce bias or description provided of those lost.