| Age ranges (years) | Frequency | Percentage (%) | Mean ± SD (years) |
| 17 - 27 | 4 | 8 | 18 ± 0.8 |
| 28 - 38 | 7 | 14 | 30 ± 0.9 |
| 39 - 49 | 9 | 18 | 41 ± 1.5 |
| 50 - 60 | 15 | 30 | 51 ± 1.9 |
| 61 - 71 | 9 | 18 | 62 ± 1.5 |
| 72 - 82 | 4 | 8 | 73 ± 0.8 |
| 83 - 93 | 2 | 4 | 83 ± 0.7 |
| Total | 50 | 100 | 51.1 ± 1.2 |