Demographics of the study population
| No | Percentage | |
| Sex | ||
| Male | 204 | 53.0 |
| Female | 181 | 47.1 |
| Age group (years) | ||
| 0–4 | 78 | 20.3 |
| 5–9 | 133 | 34.5 |
| 10–14 | 104 | 27.0 |
| 15–18 | 70 | 18.2 |
| Ethnic origin | ||
| African | 320 | 83.1 |
| Caribbean | 59 | 15.3 |
| Other | 6 | 1.6 |
| Genotype | ||
| Homozygous haemoglobin (HbSS) | 273 | 70.9 |
| HbSβ0 | 6 | 1.6 |
| HbSβ+ | 15 | 3.9 |
| Heterozygous haemoglobin | 91 | 23.6 |
| Hydroxycarbamide | ||
| Yes | 108 (104 HbSS) | 28.1 |
| No | 277 | 71.9 |
| Chronic transfusions | ||
| Yes | 27 | 7.0 |
| No | 358 | 93.0 |
| Sleep apnoea | ||
| Yes | 55 | 14.3 |
| No | 330 | 85.7 |