| Time (months) | People of investigation (cases) | Cardiothoracic ratio (%) |
| Plain control | 220 | 0.494 ± 0.018 |
| 0 - 20 | 82 | 0.496 ± 0.022 |
| 21 - 40 | 358 | 0.498 ± 0.023(1) |
| >40 | 77 | 0.499 ± 0.024(1) |