Baseline characteristics and HRs for breast cancer for potential confounders (categorical variables)
| Categorical variable | All women | HR | Lower 95% CI | Upper 95% CI | p Value |
|---|---|---|---|---|---|
| N (%) | |||||
| Ethnicity | |||||
| White | 90 011 (97.35) | ref | |||
| Black | 832 (0.90) | 1.307 | 0.622 | 2.75 | 0.48 |
| Asian | 490 (0.53) | 0.827 | 0.443 | 1.541 | 0.549 |
| Chinese | 166 (0.18) | 0.554 | 0.078 | 3.936 | 0.555 |
| Other | 669 (0.72) | 0.693 | 0.288 | 1.668 | 0.413 |
| No O-level | 56 856 (61.24) | ref | |||
| O-level | 35 986 (38.76) | 1.208 | 1.07 | 1.363 | 0.002 |
| No A-level | 78 436 (84.48) | ref | |||
| A-level | 14 406 (15.52) | 1.204 | 1.03 | 1.407 | 0.02 |
| No Clerical or commercial qualification | 67 075 (72.25) | ref | |||
| Clerical or commercial qualification | 25 767 (27.75) | 1.085 | 0.953 | 1.236 | 0.219 |
| Education | |||||
| No nursing or teaching | 79 668 (85.81) | ref | |||
| Nursing or teaching | 13 174 (14.19) | 1.051 | 0.888 | 1.243 | 0.565 |
| No degree college/university | 74 640 (80.39) | ref | |||
| Degree college/university | 18 202 (19.61) | 1 | 0.859 | 1.163 | 0.996 |
| No other than above qualification | 64 090 (69.03) | ref | |||
| Other than above qualification | 28 752 (30.97) | 0.828 | 0.724 | 0.947 | 0.006 |
| Hysterectomy with ovarian conservation at recruitment | |||||
| No | 76 318 (82.20) | ref | |||
| Yes | 16 524 (17.80) | 0.961 | 0.821 | 1.125 | 0.621 |
| Oral contraceptive pill use | |||||
| No | 37 083 (39.94) | ref | |||
| Yes | 55 759 (60.06) | 0.97 | 0.852 | 1.106 | 0.654 |
| Hormone replacement therapy use at recruitment | |||||
| No | 73 544 (79.21) | ref | |||
| Yes | 19 298 (20.79) | 1.12 | 0.971 | 1.289 | 0.118 |
| Hormone replacement therapy use at study entry | |||||
| No | 85 866 (92.50) | ref | |||
| Yes | 6963 (7.50) | 1.232 | 1 | 1.517 | 0.049 |
| Sterilisation | |||||
| No | 74 550 (80.30) | ref | |||
| Yes | 18 292 (19.70) | 0.951 | 0.817 | 1.108 | 0.523 |
| Infertility treatment | |||||
| No | 72 731 (78.34) | ref | |||
| Yes | 20 111 (21.66) | 1.459 | 1.103 | 1.93 | 0.008 |
| Pregnancies less than 6 months | |||||
| 0 | 64 126 (69,90) | ref | |||
| 1 | 18 896 (20.60) | 1.124 | 0.971 | 1.302 | 0.116 |
| 2 | 5596 (6.10) | 0.966 | 0.742 | 1.256 | 0.795 |
| 3 | 1790 (1.95) | 1.521 | 1.055 | 2.192 | 0.024 |
| 4 | 649 (0.71) | 1.690 | 0.955 | 2.990 | 0.071 |
| 5 | 678 (0.74) | 0.957 | 0.454 | 2.014 | 0.907 |
| Pregnancies more than 6 months | |||||
| 0 | 10 986 (11.87) | ref | |||
| 1 | 11 297 (12.18) | 1.023 | 0.821 | 1.276 | 0.837 |
| 2 | 40 890 (44.17) | 0.768 | 0.640 | 0.923 | 0.005 |
| 3 | 20 007 (21.61) | 0.767 | 0.624 | 0.944 | 0.012 |
| 4 | 6612 (7.14) | 0.824 | 0.626 | 1.084 | 0.625 |
| 5 | 2804 (3.03) | 0.594 | 0.386 | 0.915 | 0.385 |
| Alcohol (units per week) at study entry | |||||
| None | 21 086 (22.97) | ||||
| Less than 1 | 16 084 (17.52) | 1.011 | 0.835 | 1.226 | 0.905 |
| 1–3 | 18 717 (20.39) | 1.062 | 0.886 | 1.275 | 0.511 |
| 4–6 | 13 813 (15.05) | 1.039 | 0.851 | 1.267 | 0.71 |
| 7–10 | 11 056 (12.04) | 0.949 | 0.762 | 1.181 | 0.64 |
| 11–15 | 6549 (7.13) | 0.985 | 0.758 | 1.279 | 0.91 |
| 16–30 | 2990 (3.26) | 1.271 | 0.92 | 1.745 | 0.146 |
| 21+ | 1501 (1.64) | 1.331 | 0.866 | 2.044 | 0.192 |
| Smoking | |||||
| 0 | 51 470 (56.27) | ref | |||
| 250 | 21 661 (23.68) | 0.958 | 0.825 | 1.113 | 0.574 |
| 500 | 9632 (10.53) | 1.032 | 0.847 | 1.259 | 0.752 |
| 750 | 8706 (9.52) | 1.153 | 0.947 | 1.403 | 0.156 |
| Relatives breast cancer history | |||||
| No | 72, 731 (78.34) | ref | |||
| Yes | 20 111 (21.66) | 1.48 | 1.298 | 1.687 | <0.0005 |
| Relatives ovarian cancer history | |||||
| No | 88 878 (95.73) | ref | |||
| Yes | 3964 (4.27) | 0.946 | 0.699 | 1.279 | 0.718 |