Table 1.
Distribution of selected characteristics between cases and control participants (Mean values and standard deviations, percentiles based on distribution of variables and percentages)
| Controls (n 396) | Cases (n 396) | ||||
|---|---|---|---|---|---|
| Characteristics | n | % | n | % | P |
| Socio-demographic factors | |||||
| Age (years) | |||||
| Mean | 54·6 | 54·7 | 0·980 | ||
| sd | 12·9 | 12·9 | |||
| Ethnicity | 0·041 | ||||
| Zulu/Pedi/Xhosa/Tswana/Swazi | 66 | 16·6 | 67 | 16·9 | |
| Sotho | 144 | 36·4 | 108 | 27·3 | |
| Venda/Tsonga | 91 | 23·0 | 105 | 26·5 | |
| Ndebele | 95 | 24·0 | 116 | 29·3 | |
| Level of education | 0·078 | ||||
| None/primary | 71 | 17·9 | 97 | 24·5 | |
| High school | 279 | 70·5 | 257 | 64·9 | |
| College/University/postgraduate | 46 | 11·6 | 42 | 10·6 | |
| Individual income/month | 0·350 | ||||
| R0 | 108 | 27·3 | 125 | 31·6 | |
| R1–R3000 (n/%) | 227 | 64·2 | 219 | 59·8 | |
| R3001+ (n/%) | 61 | 8·5 | 52 | 8·6 | |
| Anthropometry | |||||
| BMI | 0·790 | ||||
| Underweight < 18·5 kg/m2 | 5 | 1·3 | 7 | 1·8 | |
| Normal weight ≥ 18·5 and ≤ 24·9 kg/m2 | 63 | 15·9 | 71 | 17·9 | |
| Overweight ≥ 25·0 and ≤ 29·9 kg/m2 | 93 | 23·5 | 87 | 21·9 | |
| Obese ≥ 30·0 kg/m2 | 235 | 59·3 | 231 | 58·4 | |
| WC (cm) | 0·011 | ||||
| Mean | 95·8 | 93·3 | |||
| sd | 13·7 | 13·8 | |||
| Lifestyle factors | |||||
| Total vigorous and moderate PA min/week | |||||
| Median | 32·1 | 39·4 | 0·303 | ||
| 25th percentile, 75th percentile | 9·1, 70·8 | 7·9, 85·8 | |||
| Current smokers | 44 | 11·1 | 35 | 8·8 | 0·286 |
| HIV positivity | 90 | 22·6 | 65 | 16·5 | 0·025 |
| Dietary factors | |||||
| TE (kJ/d) | |||||
| Median | 8990 | 9146 | 0·239 | ||
| 25th percentile, 75th percentile | 7184, 10 284 | 6812, 9759 | |||
| Protein (g/d) | 0·073 | ||||
| Median | 63·5 | 63·8 | |||
| 25th percentile, 75th percentile | 49·2, 93·1 | 47·4, 82·7 | |||
| % of TE | 12·0 | 11·8 | |||
| Fat (g/d) | 0·125 | ||||
| Median | 64·4 | 64·8 | |||
| 25th percentile, 75th percentile | 47·2, 95·7 | 42·4, 91·9 | |||
| % of TE | 27·2 | 26·9 | |||
| CHO (g/d) | 0·445 | ||||
| Mean | 338·7 | 330·8 | |||
| sd | 147·3 | 143·5 | |||
| % of TE | 64·0 | 61·4 | |||
| Dietary Fibre (g/d) | 0·616 | ||||
| Mean | 25·4 | 24·9 | |||
| sd | 11·5 | 11·0 | |||
| Added sugar (g/d) | 0·313 | ||||
| Median | 67·9 | 65·3 | |||
| 25th percentile, 75th percentile | 39·9, 109·7 | 38·4, 105·5 | |||
| % of TE | 12·0 | 12·1 | |||
| Non-alcohol consumers | 275 | 69·4 | 320 | 80·8 | <0·001 |
| Ethanol intake (g/d) | 0·005 | ||||
| Median | 4·6 | 5·4 | |||
| 25th percentile, 75th percentile | 2·5; 14·7 | 2·8; 13·8 | |||
| NOVA food groups | |||||
| Unprocessed/minimally processed foods (g/d) | |||||
| Median | 1619·4 | 1480·5 | 0·029 | ||
| 25th percentile, 75th percentile | 1115·2, 2568·0 | 1060·8, 2032·8 | |||
| Culinary ingredients (g/d) | 33·0 | 26·5 | 0·081 | ||
| Median | 16·7, 115·0 | 14·1, 77·5 | |||
| 25th percentile, 75th percentile | |||||
| Processed foods (g/d) | <0·001 | ||||
| Median | 87·1 | 63·9 | |||
| 25th percentile, 75th percentile | 28·3, 303·0 | 18·2, 172·9 | |||
| Ultra-processed foods (g/d) | |||||
| Median | 753·5 | 603·9 | <0·001 | ||
| 25th percentile, 75th percentile | 340·2, 1936·4 | 300·1, 1155·9 | |||
| Breast cancer risk factors | |||||
| Full term pregnancy in parous women | 382 | 100 | 377 | 100 | 0·374 |
| Ever breastfed in parous women | 349 | 91·3 | 339 | 89·9 | 0·293 |
| Duration of breast-feeding (1) (months) | 32 | 12, 60 | 30 | 8, 58 | 0·187 |
| Use of birth control (contraceptives) | 215 | 54,3 | 229 | 57·8 | 0·316 |
| Postmenopausal | 257 | 64·8 | 248 | 62·6 | 0·852 |
| Age at menopause (2) (years) | 48 | 44, 50 | 47 | 42, 50 | 0·331 |
| Family history of BC | 17 | 4·3 | 25 | 6·3 | 0·205 |
| Age at menarche | |||||
| Median | 15 | 15 | 0·537 | ||
| 25th percentile, 75th percentile | 13, 16 | 13, 16 | |||
| Breast cancer case characteristics | |||||
| Stage at BC diagnoses | |||||
| I | – | 24 | 6·5 | ||
| II | – | 175 | 44·8 | ||
| III | – | 161 | 40·8 | ||
| IV | – | 31 | 7·9 | ||
| Receptor status | |||||
| ER+ | – | 298 | 75·2 | – | |
| PR+ | – | 263 | 66·4 | – | |
| HER2 | – | 114 | 28·8 | – | |
| Breast cancer subtype† | |||||
| HER2 enriched | – | 21 | 5·3 | – | |
| Luminal A | – | 40 | 10·1 | – | |
| Luminal B | – | 269 | 67·9 | – | |
| TNBC | – | 64 | 16·2 | – | |
WC, waist circumference; TE, total energy; CHO, carbohydrates; PA, physical activity; ER+, oestrogen receptor positive; PR+ progesterone receptor positive; HER2, human-epidermal growth factor-2; TNBC, triple negative breast cancer; HRT, hormone replacement therapy.
Continuous variables are presented as means and standard deviations if normally distributed and median (25th percentile, 75th percentile) if not, categorical variables are presented as percentages.
* 16 Missing values for menopausal status (15 cases and 1 control). Missing values were excluded from percentage calculations
Defined using Allred score.
(1) In breast-feeding women only.
(2) Among postmenopausal women only.