Table 1. Demographic and epidemiological characteristics of breast cancer patients and associations with breast cancer prognosis.
| Characteristics | N=2647 | Stage I | Stage II | Overall survival | Disease-free survival | |||
| (%) | (N=1297, %) | (N=1350, %) | HR (95% CI) | P | HR (95% CI) | P | ||
| Age at diagnosis (years) | ||||||||
| ≤50 | 1167 (44.1) | 578 (44.6) | 589 (43.7) | 1 (ref) | <0.001 | 1 (ref) | 0.016 | |
| >50 | 1477 (55.9) | 717 (55.4) | 760 (56.3) | 1.655 (1.264-2.168) | 1.320 (1.052-1.657) | |||
| BMI (kg/m2) | ||||||||
| ≤18.4 | 56 (2.1) | 30 (2.4) | 26 (1.9) | 0.900 (0.330-2.457) | 0.203 | 0.718 (0.293-1.759) | 0.634 | |
| 18.5-23.9 | 1025 (39.3) | 512 (40.4) | 513 (38.4) | 1 (ref) | 1 (ref) | |||
| 24.0-27.9 | 1024 (39.3) | 508 (40.1) | 516 (38.6) | 1.291 (0.962-1.733) | 1.105 (0.858-1.423) | |||
| ≥28 | 500 (19.2) | 218 (17.2) | 283 (21.1) | 1.386 (0.975-1.971) | 1.142 (0.838-1.556) | |||
| Marital status | ||||||||
| Unmarried | 35 (1.3) | 16 (1.2) | 19 (1.4) | 1 (ref) | 0.593 | 1 (ref) | 0.850 | |
| Married | 2420 (92.9) | 1180 (91.8) | 1240 (93.9) | 0.939 (0.300-2.934) | 1.186 (0.380-3.701) | |||
| Divorced/widowed | 150 (5.8) | 89 (6.9) | 61 (4.6) | 1.213 (0.355-4.139) | 1.329 (0.393-4.493) | |||
| Education | ||||||||
| Without education | 133 (5.3) | 71 (5.7) | 62 (5.0) | 1 (ref) | 0.001 | 1 (ref) | 0.079 | |
| Primary school | 303 (12.1) | 154 (12.3) | 149 (12.0) | 0.615 (0.357-1.056) | 0.656 (0.386-1.116) | |||
| Junior high school | 738 (29.6) | 364 (29.1) | 374 (30.1) | 0.399 (0.243-0.658) | 0.563 (0.352-0.902) | |||
| High school | 810 (32.5) | 426 (34.0) | 384 (30.9) | 0.425 (0.261-0.693) | 0.545 (0.342-0.869) | |||
| College and advanced | 512 (20.5) | 238 (19.0) | 274 (22.0) | 0.372 (0.218-0.634) | 0.520 (0.318-0.852) | |||
| Average monthly income (RMB) | ||||||||
| ≤999 | 839 (34.5) | 480 (38.8) | 359 (30.0) | 1 (ref) | 0.056 | 1 (ref) | 0.112 | |
| 1000-1999 | 1055 (43.3) | 544 (43.9) | 511 (42.8) | 0.895 (0.667-1.202) | 0.995 (0.766-1.293) | |||
| ≥2000 | 539 (22.2) | 214 (17.3) | 325 (27.2) | 0.616 (0.414-0.919) | 0.718 (0.510-1.012) | |||
| Occupation | ||||||||
| No | 1459 (58.3) | 770 (61.3) | 689 (55.3) | 1 (ref) | 0.009 | 1 (ref) | 0.089 | |
| Yes | 1042 (41.7) | 486 (38.7) | 556 (44.7) | 0.689 (0.520-0.912) | 0.814 (0.641-1.033) | |||
| Age at marriage (years) | ||||||||
| <30 | 2441 (93.9) | 1202 (94.1) | 1239 (93.8) | 1 (ref) | 0.816 | 1 (ref) | 0.457 | |
| ≥30 | 158 (6.1) | 76 (5.9) | 82 (6.2) | 0.940 (0.556-1.587) | 0.831 (0.509-1.355) | |||
| Age at menarche (years) | ||||||||
| ≤14 | 698 (26.6) | 347 (27.0) | 351 (26.2) | 1 (ref) | 0.015 | 1 (ref) | 0.117 | |
| >14 | 1927 (73.4) | 938 (73.0) | 989 (73.8) | 1.466 (1.075-1.999) | 1.231 (0.949-1.596) | |||
| Number of pregnancies | ||||||||
| ≤2 | 1198 (45.5) | 576 (44.7) | 622 (46.2) | 1 (ref) | 0.385 | 1 (ref) | 0.695 | |
| >2 | 1435 (54.5) | 712 (55.3) | 723 (53.8) | 1.120 (0.867-1.448) | 1.045 (0.837-1.305) | |||
| Number of live births | ||||||||
| ≤1 | 1585 (62.0) | 783 (62.4) | 802 (61.6) | 1 (ref) | <0.001 | 1 (ref) | 0.002 | |
| >1 | 971 (38.0) | 471 (37.6) | 500 (38.4) | 1.760 (1.358-2.280) | 1.435 (0.143-1.802) | |||
| Breastfeeding duration (months) | ||||||||
| ≤12 | 1045 (42.0) | 534 (43.9) | 511 (40.1) | 1 (ref) | 0.028 | 1 (ref) | 0.010 | |
| >12 | 1444 (58.0) | 682 (56.1) | 762 (59.9) | 1.366 (1.033-1.804) | 1.372 (1.079-1.746) | |||
| Abortion | ||||||||
| No | 732 (28.2) | 357 (28.1) | 375 (28.2) | 1 (ref) | 0.003 | 1 (ref) | 0.004 | |
| Yes | 1867 (71.8) | 914 (71.9) | 953 (71.8) | 0.664 (0.508-0.868) | 0.705 (0.556-0.893) | |||
| Oral contraceptive | ||||||||
| No | 2036 (82.6) | 1007 (81.5) | 1029 (83.7) | 1 (ref) | 0.823 | 1 (ref) | 0.673 | |
| Yes | 428 (17.4) | 228 (18.5) | 200 (16.3) | 1.040 (0.738-1.465) | 0.935 (0.684-1.278) | |||
| Menopause | ||||||||
| No | 1247 (47.4) | 614 (47.6) | 633 (47.2) | 1 (ref) | <0.001 | 1 (ref) | 0.011 | |
| Yes | 1385 (52.6) | 677 (52.4) | 708 (52.8) | 1.844 (1.408-2.417) | 1.341 (1.070-1.679) | |||
| BBD | ||||||||
| No | 1909 (73.6) | 957 (74.2) | 952 (72.9) | 1 (ref) | 0.227 | 1 (ref) | 0.028 | |
| Yes | 686 (26.4) | 332 (25.8) | 354 (27.1) | 0.829 (0.611-1.125) | 0.741 (0.566-0.968) | |||
| Smoking | ||||||||
| No | 2214 (88.0) | 1108 (88.2) | 1106 (87.8) | 1 (ref) | 0.988 | 1 (ref) | 0.428 | |
| Yes | 302 (12.0) | 148 (11.8) | 154 (12.2) | 1.003 (0.671-1.500) | 1.151 (0.812-1.632) | |||
| Alcohol drinking | ||||||||
| No | 2445 (97.4) | 1233 (98.0) | 1212 (96.8) | 1 (ref) | 0.573 | 1 (ref) | 0.246 | |
| Yes | 65 (2.6) | 25 (2.0) | 40 (3.2) | 0.574 (0.280-2.025) | 0.562 (0.209-1.508) | |||
| Physical activity per week (hours) | ||||||||
| ≤3 | 1817 (72.9) | 943 (75.3) | 874 (70.5) | 1 (ref) | 0.072 | 1 (ref) | 0.067 | |
| >3 | 675 (27.1) | 310 (24.7) | 365 (29.5) | 1.295 (0.976-1.718) | 1.261 (0.984-1.617) | |||
| Family history of cancer | ||||||||
| No | 1817 (69.1) | 912 (70.4) | 905 (67.8) | 1 (ref) | 0.117 | 1 (ref) | 0.258 | |
| Yes | 814 (30.9) | 384 (29.6) | 430 (32.2) | 0.795 (0.596-1.060) | 0.868 (0.678-1.110) | |||
BMI, body mass index; BBD, benign breast disease; HR, hazard ratio; CI, confidence interval.