Characteristic of the study population
| Breast cancer cases | Cancer-free controls | |
|---|---|---|
| No. of individuals | 8,067 | 13,129 |
| Age (median and range) | 50 (19–98) | 33 (18–84) |
| Age (mean ± SD) | 51.1 ± 11.6 | 34.8 ± 9.3 |
| Ethnicity | ||
| Han | 7,727 (95.8%) | 12,288 (93.6%) |
| Non-han | 340 (4.2%) | 841 (6.4%) |