Table 7.
Predictors of thinness and low %BF from univariate logistic regression analyses for 18-year-old men and women, Johannesburg–Soweto, South Africa, Birth to Twenty Plus (Bt20+) cohort
| Thinness† (men) | Thinness† (women) | Low %BF‡ (men) | Low %BF‡ (women) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| n | % | OR | 95 % CI | n | % | OR | 95 % CI | n | % | OR | 95 % CI | n | % | OR | 95 % CI | |
| Intrinsic factors | ||||||||||||||||
| Age | 894 | P=0·48 | 771 | P=0·80 | 795 | P=0·004** | 676 | P=0·001** | ||||||||
| 17–18 years§ | 316 | 22·8 | 1·00 | – | 311 | 14·8 | 1·00 | – | 282 | 56·4 | 1·00 | – | 283 | 12·4 | 1·00 | – |
| ≥18 years | 578 | 24·9 | 1·12 | 0·81, 1·55 | 460 | 14·1 | 0·95 | 0·63, 1·43 | 513 | 66·7 | 1·54 | 1·15, 2·08 | 393 | 22·9 | 2·10 | 1·38, 3·22 |
| Population group | 882 | P=0·0001*** | 761 | P=0·0002*** | 787 | P=0·014* | 671 | P=0·003** | ||||||||
| Black African§ | 740 | 23·2 | 1·00 | – | 611 | 11·8 | 1·00 | – | 661 | 62·2 | 1·00 | – | 543 | 16·0 | 1·00 | – |
| White | 51 | 3·9 | 0·13 | 0·03, 0·56 | 52 | 19·2 | 1·78 | 0·86, 3·71 | 52 | 55·8 | 0·77 | 0·43, 1·35 | 51 | 31·4 | 2·39 | 1·27, 4·52 |
| Mixed ancestry | 91 | 38·5 | 2·06 | 1·31, 3·25 | 98 | 27·5 | 2·85 | 1·71, 4·72 | 74 | 78·4 | 2·20 | 1·24, 3·91 | 77 | 27·3 | 1·96 | 1·13, 3·41 |
| Low birth weight (<2500 g) | 831 | P=0·004** | 714 | P=0·19 | 789 | P=0·045* | 673 | P=0·99 | ||||||||
| No§ | 744 | 22·7 | 1·00 | – | 620 | 14 | 1·00 | – | 710 | 61·8 | 1·00 | – | 587 | 18·6 | 1·00 | – |
| Yes | 87 | 36·8 | 1·98 | 1·24, 3·16 | 94 | 19·1 | 1·45 | 0·83, 2·54 | 79 | 73·4 | 1·70 | 1·01, 2·87 | 86 | 18·6 | 1·00 | 0·56, 1·79 |
| Pubertal development | 724 | P=0·94 | 674 | P=0·11 | 703 | P=0·44 | 635 | P=0·06(*) | ||||||||
| Early stage§,|| | 104 | 23·1 | 1·00 | – | 263 | 11·4 | 1·00 | – | 91 | 64·8 | 1·00 | – | 247 | 13·8 | 1·00 | – |
| Late stage¶ | 620 | 22·7 | 0·98 | 0·60, 1·61 | 411 | 15·8 | 1·46 | 0·92, 2·32 | 612 | 60·6 | 0·83 | 0·53, 1·32 | 388 | 19·6 | 1·53 | 0·98, 2·37 |
| Household socio-economic factors | ||||||||||||||||
| Caregiver education | 805 | P=0·61 | 696 | P=0·93 | 716 | P=0·004** | 612 | P=0·29 | ||||||||
| ≤Primary school | 123 | 27·6 | 1·30 | 0·70, 2·42 | 99 | 15·1 | 1·16 | 0·53, 2·55 | 111 | 67·6 | 2·36 | 1·34, 4·15 | 89 | 15·7 | 0·59 | 0·28, 1·24 |
| Secondary school | 585 | 23·8 | 1·06 | 0·64, 1·77 | 492 | 14·4 | 1·09 | 0·59, 2·03 | 509 | 63·5 | 1·97 | 1·27, 3·05 | 427 | 17·8 | 0·69 | 0·40, 1·17 |
| Higher education§ | 97 | 22·7 | 1·00 | – | 105 | 13·3 | 1·00 | – | 96 | 46·9 | 1·00 | – | 96 | 24·0 | 1·00 | – |
| Household wealth index | 790 | P=0·009** | 681 | P=0·021* | 701 | P=0·39 | 593 | P=0·71 | ||||||||
| 1st tertile | 291 | 25·8 | 1·81 | 1·16, 2·84 | 234 | 9·4 | 0·48 | 0·27, 0·84 | 263 | 65·8 | 1·31 | 0·89, 1·93 | 204 | 16·7 | 0·81 | 0·48, 1·35 |
| 2nd tertile | 281 | 27·0 | 1·94 | 1·24, 3·03 | 227 | 17·2 | 0·96 | 0·59, 1·57 | 253 | 63·2 | 1·17 | 0·79, 1·73 | 197 | 18·8 | 0·94 | 0·57, 1·55 |
| 3rd tertile (high)§ | 218 | 16·1 | 1·00 | – | 220 | 17·7 | 1·00 | – | 185 | 59·5 | 1·00 | – | 192 | 19·8 | 1·00 | – |
| Adolescent smoking status | 652 | P=0·68 | 586 | P=0·90 | 616 | P=0·035* | 551 | P=0·96 | ||||||||
| Never smoked§ | 160 | 23·8 | 1·00 | – | 219 | 14·2 | 1·00 | – | 159 | 57·2 | 1·00 | – | 215 | 18·1 | 1·00 | – |
| Previous smoker | 192 | 21·9 | 0·89 | 0·54, 1·48 | 232 | 15·5 | 1·11 | 0·66, 1·87 | 175 | 57·1 | 0·99 | 0·64, 1·54 | 208 | 18·3 | 1·01 | 0·61, 1·65 |
| Current smoker | 300 | 25·3 | 1·09 | 0·69, 1·70 | 135 | 14·1 | 0·99 | 0·54, 1·84 | 282 | 67·4 | 1·54 | 1·03, 2·30 | 128 | 17·2 | 0·94 | 0·53, 1·66 |
| Neighbourhood socio-economic factors | ||||||||||||||||
| Neighbourhood economic index | 826 | P=0·47 | 721 | P=0·70 | 731 | P=0·94 | 633 | P=0·38 | ||||||||
| 1st tertile | 268 | 22·4 | 1·05 | 0·70, 1·57 | 266 | 14·7 | 0·92 | 0·57, 1·51 | 242 | 63·2 | 1·02 | 0·71, 1·48 | 239 | 15·5 | 0·72 | 0·44, 1·17 |
| 2nd tertile | 280 | 25·7 | 1·26 | 0·85, 1·86 | 225 | 12·9 | 0·79 | 0·47, 1·35 | 240 | 64·2 | 1·07 | 0·74, 1·54 | 187 | 19·3 | 0·94 | 0·57, 1·54 |
| 3rd tertile (high)§ | 278 | 21·6 | 1·00 | – | 230 | 15·6 | 1·00 | – | 249 | 62·6 | 1·00 | – | 207 | 20·3 | 1·00 | – |
| Neighbourhood availability of services index | 822 | P=0·36 | 723 | P=0·43 | 728 | P=0·34 | 636 | P=0·72 | ||||||||
| 1st tertile | 278 | 24·8 | 1·30 | 0·87, 1·93 | 234 | 12·8 | 0·73 | 0·43, 1·22 | 249 | 67·1 | 1·29 | 0·89, 1·86 | 219 | 16·4 | 0·87 | 0·52, 1·44 |
| 2nd tertile | 268 | 24·6 | 1·28 | 0·86, 1·92 | 257 | 13·6 | 0·78 | 0·47, 1·28 | 234 | 62 | 1·03 | 0·71, 1·49 | 222 | 19·4 | 1·06 | 0·65, 1·73 |
| 3rd tertile (high)§ | 276 | 20·3 | 1·00 | – | 232 | 16·8 | 1·00 | – | 245 | 61·2 | 1·00 | – | 195 | 18·5 | 1·00 | – |
| Neighbourhood problem index | 819 | P=0·09(*) | 714 | P=0·60 | 723 | P=0·31 | 624 | P=0·29 | ||||||||
| 1st tertile | 289 | 27·3 | 1·53 | 1·02, 2·29 | 230 | 12·6 | 0·77 | 0·46, 1·29 | 251 | 66·1 | 1·32 | 0·91, 1·92 | 210 | 17·1 | 0·78 | 0·48, 1·28 |
| 2nd tertile | 282 | 22·0 | 1·14 | 0·75, 1·74 | 229 | 13·5 | 0·84 | 0·51, 1·40 | 244 | 64·8 | 1·24 | 0·86, 1·80 | 193 | 15 | 0·67 | 0·40, 1·12 |
| 3rd tertile (low)§ | 248 | 19·8 | 1·00 | – | 255 | 15·7 | 1·00 | – | 228 | 59·7 | 1·00 | – | 221 | 20·8 | 1·00 | – |
| Neighbourhood social support index | 826 | P=0·18 | 720 | P=0·26 | 731 | P=0·78 | 633 | P=0·65 | ||||||||
| 1st tertile | 247 | 21·5 | 0·74 | 0·50, 1·10 | 262 | 11·8 | 0·65 | 0·39, 1·09 | 208 | 62 | 0·99 | 0·68, 1·44 | 231 | 16·5 | 0·89 | 0·55, 1·47 |
| 2nd tertile | 281 | 21·0 | 0·72 | 0·49, 1·06 | 235 | 14·5 | 0·82 | 0·50, 1·36 | 261 | 64·8 | 1·11 | 0·78, 1·59 | 191 | 19·9 | 1·13 | 0·69, 1·86 |
| 3rd tertile (favourable)§ | 298 | 26·9 | 1·00 | – | 223 | 17·0 | 1·00 | – | 262 | 62·2 | 1·00 | – | 211 | 18·0 | 1·00 | – |
| Place of residence | 723 | P=0·13 | 626 | P=0·097(*) | 636 | P=0·42 | 552 | P=0·075(*) | ||||||||
| Soweto§ | 617 | 23·7 | 1·00 | – | 498 | 13·6 | 1·00 | – | 537 | 63·9 | 1·00 | – | 439 | 16·7 | 1·00 | – |
| Metropolitan Johannesburg | 106 | 17·0 | 0·66 | 0·38, 1·13 | 128 | 19·5 | 1·53 | 0·92, 2·55 | 99 | 59·6 | 0·83 | 0·54, 1·29 | 113 | 23·9 | 1·57 | 0·95, 2·59 |
%BF, percentage body fat.
(*) P<0·10, *P<0·05, **P<0·01, ***P<0·001.
†
Thinness was defined using age- and sex-specific international cut-offs for BMI for <18 years( 47 ) and ≥18 years( 48 ).
‡
Low %BF was defined as fat mass ≤15·00th percentile( 49 ).
§
Reference category.
||
In men, early stage of pubertal development refers to Tanner stages 2–3 (late maturers). In women, it refers to age of entry into menarche <13 years (early maturers).
¶
In men, late stage of pubertal development refers to Tanner stages 4–5 (early maturers). In women, it refers to age of entry into menarche ≥13 years (late maturers).