|
Demographic and hormone-related risk factors |
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| Variables |
Cases by availability of ER/PR information |
Controls |
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|
|
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| Cases with known receptor status |
Cases with borderline positive/undecided status |
Cases without information |
p for comparison across the three case groups |
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|
|
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| Number of subjects |
1,366 (79.2%) |
83 (4.8%) |
276 (16.0%) |
440 |
|
| Mean age at reference date (SD), years |
42.5 (5.4) |
42.8 (5.2) |
44.0 (4.6) |
0.0001a,b |
42.6 (4.9) |
| Race |
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| White |
1,206 (88.3%) |
77 (92.8%) |
238 (86.2%) |
405 (92.0%) |
|
| African-American |
160 (11.7%) |
6 (7.2%) |
38 (13.8%) |
0.26c |
35 (8.0%) |
| Education |
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| High school or lower |
262 (19.2%) |
19 (22.9%) |
76 (27.5%) |
60 (13.6%) |
|
| Technical school or some college |
489 (35.8%) |
28 (33.7%) |
103 (37.3%) |
150 (34.1%) |
|
| College graduate |
615 (45.0%) |
36 (43.4%) |
97 (35.2%) |
0.01c,d |
230 (52.3%) |
| First-degree breast cancer family history |
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| No |
1,091 (79.9%) |
63 (75.9%) |
224 (81.1%) |
388 (88.2%) |
|
| Yes |
229 (16.7%) |
19 (22.9%) |
46 (16.7%) |
41 (9.3%) |
|
| Unknowne |
46 (3.4%) |
1 (1.2%) |
6 (2.2%) |
0.39c |
11 (2.5%) |
| Mean age at menarche (SD), years |
12.4 (1.5) |
12.6 (1.7) |
12.4 (1.4) |
0.51a |
12.7 (1.5) |
| Ever had a full-term (>26-week) pregnancy |
66.6% |
74.7% |
68.5% |
0.28c |
71.6% |
| Mean number of full-term pregnancies (SD) |
2.1 (1.0) |
2.1 (1.1) |
2.1 (0.9) |
0.92a |
2.2 (1.1) |
| Mean age at first full-term pregnancy (SD) |
26.7 (6.4) |
26.2 (6.2) |
24.9 (5.8) |
0.002a,b |
27.1 (6.2) |
| Ever breastfed among parous women |
80.4% |
77.4% |
70.9% |
0.01c,d |
87.9% |
| Mean duration of breastfeeding (all pregnancies) among those who breastfed (SD), months |
14.2 (16.3) |
13.7 (13.6) |
12.6 (14.6) |
0.56a |
16.6 (17.3) |
| Mean BMI 1 year before reference date (SD), kg/m2 |
25.8 (6.1) |
26.2 (6.4) |
26.6 (6.5) |
0.12a |
25.7 (6.4) |
| Ever used COC |
85.9% |
84.3% |
85.9% |
0.92c |
89.3% |
| Mean duration of COC use among users (SD), years |
6.9 (6.3) |
5.8 (6.6) |
6.4 (6.4) |
0.23a |
6.7 (6.2) |
| Alcohol drinking status during reference age |
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| Never |
428 (31.3%) |
34 (41.0%) |
96 (37.8%) |
141 (32.1%) |
|
| Former |
259 (19.0%) |
16 (19.3%) |
53 (19.2%) |
90 (20.5%) |
|
| Current |
679 (49.7%) |
33 (39.7%) |
127 (46.0%) |
0.30c |
209 (47.5%) |
| Alcohol drinking status in recent 5-year period |
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| No |
428 (31.3%) |
34 (41.0%) |
96 (34.8%) |
141 (32.1%) |
|
| Yes |
759 (55.6%) |
40 (48.2%) |
137 (49.6%) |
228 (51.8%) |
|
| Yes, but not in the five year period |
179 (13.1%) |
9 (10.8%) |
43 (15.6%) |
0.17c |
71 (16.1%) |
| Mean number of alcoholic drinks per week in recent 5 years for drinkers (SD) |
6.6 (20.1) |
4.9 (6.1) |
6.0 (8.4) |
0.80a |
4.6 (9.1) |
|
Results are for 1,725 case patients and 440 control subjects. BMI, body mass index; COC, combined oral contraceptive; ER/PR, estrogen receptor and progesterone receptor; SD, standard deviation. aF test. bBonferroni t tests for pairwise comparisons: p values for cases with complete ER/PR information versus cases without ER/PR information ≤ 0.001, and p values for the other comparisons ≥ 0.20. cPearson χ2 test. dPearson χ2 tests for pairwise comparisons: p values for cases with complete ER/PR information versus cases without ER/PR information ≤ 0.004, and p values for the other comparisons ≥ 0.32. eUnknown category was excluded from Pearson χ2 tests. | |||||
Ma et al. Breast Cancer Research 2006 8:R39 doi:10.1186/bcr1514 |
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