Table 2. Demographic and Other Breast Cancer Risk Factors, By Genotyping Stage, the Shanghai Breast Cancer Genetics Study.
| Characteristics | Study Stage 1 (4,227) | Study Stage 2 (N=6,270) | By Genotyping Status (N=11,585) | ||||||
|---|---|---|---|---|---|---|---|---|---|
|
|
|
|
|||||||
| Cases (N=2,079) | Controls (N=2,148) | p-value | Cases (N=4,419) | Controls (N=1,851) | p-value | Genotyped (N=10,497) | Not Genotyped (N=1,088) | p-value | |
| Demographic Factors | |||||||||
| Age (years) | 49.3 ± 8.3 | 49.1 ± 8.7 | 0.390 | 53.9 ± 10.2 | 53.3 ± 8.8 | 0.016 | 51.8 ± 9.5 | 50.6 ± 9.1 | <0.001 |
| Education (less than middle school) | 206 (9.9%) | 286 (13.3%) | <0.001 | 525 (11.9%) | 304 (16.4%) | <0.001 | 1,255 (12.0%) | 163 (15.0%) | 0.004 |
| Reproductive Risk Factors | |||||||||
| Age at menarche (years) | 14.5 ± 1.7 | 14.7 ± 1.8 | <0.001 | 14.4 ± 1.7 | 14.7 ±1.8 | <0.001 | 14.5 ± 1.7 | 14.5 ±1.7 | 0.902 |
| Postmenopausal | 804 (38.8%) | 873 (40.7%) | 0.195 | 2,257 (51.1%) | 1,047 (56.6%) | <0.001 | 4,988 (47.5%) | 507 (46.6%) | 0.572 |
| Age at menopause (years) 1 | 48.4 ± 4.5 | 47.7 ± 4.8 | 0.002 | 49.0 ± 4.3 | 48.8 ± 4.1 | 0.162 | 48.6 ± 4.4 | 48.2 ± 4.5 | 0.042 |
| Age at first live birth (years) 2 | 26.5 ± 3.9 | 26.0 ± 3.8 | 0.001 | 26.8 ± 3.9 | 25.5 ± 4.0 | <0.001 | 26.8 ± 3.8 | 26.6 ± 4.2 | 0.158 |
| Use of oral contraceptives 3 | 419 (20.2%) | 433 (20.2%) | 0.997 | 166 (17.2%) | 416 (22.5%) | 0.001 | 1,434 (20.4%) | 205 (20.9%) | 0.696 |
| Additional Risk Factors | |||||||||
| First degree relative with breast cancer | 92 (4.4%) | 63 (2.9%) | 0.010 | 246 (5.6%) | 24 (2.6%) | <0.001 | 447 (4.3%) | 37 (3.4%) | 0.182 |
| Use of hormone replacement therapy 4 | 65 (3.1%) | 51 (2.4%) | 0.136 | 161 (5.7%) | 70 (3.8%) | 0.003 | 347 (3.9%) | 26 (2.7%) | 0.054 |
| History of breast fibroadenomas 5 | 201 (9.7%) | 121 (5.6%) | <0.001 | 96 (10.0%) | 48 (5.1%) | <0.001 | 514 (7.3%) | 67 (6.9%) | 0.614 |
| Body mass index (kg/m2) | 23.8 ± 3.3 | 23.3 ± 3.4 | <0.001 | 24.0 ± 3.5 | 23.6 ± 3.3 | <0.001 | 23.7 ± 3.4 | 23.3 ± 3.4 | <0.001 |
| Waist-to-hip ratio | 0.822 ± 0.06 | 0.808 ± 0.06 | <0.001 | 0.834 ± 0.05 | 0.816 ± 0.05 | <0.001 | 0.823 ± 0.06 | 0.812 ± 0.05 | <0.001 |
| Regular physical activity | 521 (25.1%) | 638 (29.7%) | <0.001 | 2,473 (56.0%) | 622 (33.6%) | <0.001 | 4,245 (40.5%) | 299 (27.5%) | <0.001 |
Continuous variables: mean values ± standard deviation, p-value from t-tests; Categorical variables: numbers and percentages, p-values from χ2 test
1
Among postmenopausal women
2
Among parous women
3
Information unavailable for 3,456 participants genotyped in Stage 2
4
Information unavailable for 1,601 participants genotyped in Stage 2
5
Information unavailable for 4,375 participants genotyped in Stage 2
Bold values considered to be significant p≤0.05