Table 1 General information on subject children and response rates in Beijing, Chongqing, and Guangzhou
Characteristic | Beijing | Chongqing | Guangzhou | Total | Â | |||
|---|---|---|---|---|---|---|---|---|
| Â | n | % | n | % | n | % | n | % |
Number of children | 10,372 | 42.70% | 9,846 | 40.53% | 4,072 | 16.77% | 24,290 | Â |
Response rate | 98.60% | Â | 97.21% | Â | 90.90% | Â | 96.62% | Â |
Gender | Â | Â | Â | Â | Â | Â | Â | Â |
   Male | 5,455 | 52.59% | 5,258 | 53.40% | 2,195 | 53.90% | 12,908 | 53.14% |
   Female | 4,917 | 47.41% | 4,588 | 46.60% | 1,877 | 46.10% | 11,382 | 46.86% |
Age (mean ± SD) | 7.63 ± 4.04 |  | 8.74 ± 2.72 |  | 8.39 ± 3.53 |  | 8.20 ± 3.51 |  |