Table 2.
Sociodemographic characteristics of the sample: adolescents aged 17–19 years, Johannesburg–Soweto, South Africa, Birth to Twenty Plus (Bt20+) cohort
| Total group (n 2019) | Men (n 974) | Women (n 1045) | |||||
|---|---|---|---|---|---|---|---|
| Variable | Mean | sd | Mean | sd | Mean | sd | Test |
| Intrinsic factors | |||||||
| Age (years) | 18·21 | 0·57 | 18·24 | 0·58 | 18·18 | 0·57 | P=0·03*† |
| Age of entry into menarche (years) | – | – | – | – | 12·70 | 1·25 | – |
| Birth weight (kg) | 3·11 | 0·51 | 3·11 | 0·52 | 3·01 | 0·49 | P<0·0001***† |
| n | % | n | % | n | % | ||
| Population group | |||||||
| White | 136 | 6·7 | 65 | 6·7 | 71 | 6·8 | P=0·85‡ |
| Black African | 1638 | 81·1 | 792 | 81·3 | 846 | 80·9 | |
| Mixed ancestry | 218 | 10·8 | 102 | 10·5 | 116 | 11·1 | |
| Indian/Asian | 27 | 1·3 | 15 | 1·5 | 12 | 1·2 | |
| Physical maturation (Tanner stages) | |||||||
| Early stages (2–3) | – | – | 111 | 14·1 | – | – | – |
| Later stages (4–5) | – | – | 676 | 85·9 | – | – | |
| Age of entry into menarche | |||||||
| 9–13 (years) | – | – | – | – | 397 | 43·1 | – |
| 13–17 (years) | – | – | – | – | 523 | 56·8 | |
| Low birth weight (<2500 g) | |||||||
| No | 1674 | 89·0 | 818 | 90·2 | 856 | 87·9 | P=0·11‡ |
| Yes | 207 | 11·0 | 89 | 9·8 | 118 | 12·1 | |
| Household socio-economic factors | |||||||
| Caregiver education | |||||||
| Less than or primary school | 265 | 14·6 | 131 | 14·9 | 134 | 14·3 | P=0·78‡ |
| Secondary school | 1296 | 71·4 | 629 | 71·6 | 667 | 71·2 | |
| Higher education | 254 | 14·0 | 118 | 13·5 | 136 | 14·5 | |
| Adolescent smoking status | |||||||
| Never smoked | 485 | 32·0 | 176 | 24·6 | 309 | 38·6 | P<0·0001***‡ |
| Previous smoker | 521 | 34·4 | 215 | 30·1 | 306 | 38·2 | |
| Current smoker | 509 | 33·6 | 323 | 45·2 | 186 | 23·2 | |
| Household wealth index | |||||||
| 1st tertile | 612 | 34·3 | 305 | 35·4 | 307 | 33·3 | P=0·41‡ |
| 2nd tertile | 612 | 34·3 | 299 | 34·7 | 313 | 34·0 | |
| 3rd tertile | 558 | 31·4 | 257 | 29·9 | 301 | 32·7 | |
| Neighbourhood socio-economic factors | |||||||
| Place of residence | |||||||
| Soweto | 1338 | 82·1 | 664 | 84·4 | 674 | 80·0 | P=0·02*‡ |
| Metropolitan Johannesburg | 291 | 17·9 | 123 | 15·6 | 168 | 20·0 | |
| Neighbourhood economic index | |||||||
| 1st tertile | 663 | 35·2 | 293 | 32·5 | 370 | 37·7 | P=0·06(*) ‡ |
| 2nd tertile | 590 | 31·3 | 296 | 32·9 | 294 | 29·9 | |
| 3rd tertile (high) | 630 | 33·5 | 312 | 34·6 | 318 | 32·4 | |
| Neighbourhood availability of services index | |||||||
| 1st tertile | 627 | 33·4 | 297 | 33·1 | 330 | 33·6 | P=0·50‡ |
| 2nd tertile | 641 | 34·1 | 297 | 33·1 | 344 | 35·0 | |
| 3rd tertile (high) | 611 | 32·5 | 303 | 33·8 | 308 | 31·4 | |
| Neighbourhood problem index | |||||||
| 1st tertile | 623 | 33·5 | 307 | 34·3 | 316 | 32·6 | P=0·22‡ |
| 2nd tertile | 617 | 33·1 | 306 | 34·2 | 311 | 32·1 | |
| 3rd tertile (low) | 622 | 33·4 | 281 | 31·5 | 341 | 35·3 | |
| Neighbourhood social support index | |||||||
| 1st tertile | 622 | 33·1 | 270 | 29·9 | 352 | 35·9 | P=0·02*‡ |
| 2nd tertile | 629 | 33·4 | 308 | 34·2 | 321 | 32·8 | |
| 3rd tertile (favourable) | 631 | 33·5 | 324 | 35·9 | 307 | 31·3 | |
(*) P<0·10, *P<0·05, **P<0·01, ***P<0·001.
†
P value from t test.
‡
P value from χ 2 test.