Table 2.
Baseline characteristics of study population by age
| |
Age <55 years |
Age 55 to 64 years |
Age ≥65 years |
|||
|---|---|---|---|---|---|---|
| Cases | Controls | Cases | Controls | Cases | Controls | |
|
N |
1,533 |
3,373 |
1,021 |
2,031 |
860 |
1,795 |
| Percent mammographic density |
40.7 (19.6) |
33.6 (20.2) |
29.2 (18.0) |
23.7 (17.6) |
24.8 (17.1) |
21.1 (16.2) |
| Age at mammogram |
47.3 (4.5) |
47.4 (4.4) |
59.4 (2.9) |
59.4 (2.9) |
71.0 (5.2) |
71.2 (5.1) |
| Age at diagnosis |
51.8 (5.6) |
– |
63.8 (4.1) |
– |
75.0 (5.5) |
– |
| Body mass index |
24.4 (6.5) |
25.4 (6.3) |
26.1 (7.1) |
26.2 (5.6) |
25.6 (8.5) |
26 (5.6) |
| Body mass index categories (kg/m2) | ||||||
| <25 |
845 (55.1%) |
1,902 (56.4%) |
438 (42.9%) |
964 (47.5%) |
322 (37.4%) |
849 (47.3%) |
| 25 to 29 |
432 (28.2%) |
831 (24.6%) |
332 (32.5%) |
642 (31.6%) |
262 (30.5%) |
602 (33.5%) |
| 30 to 34 |
130 (8.5%) |
352 (10.4%) |
138 (13.5%) |
275 (13.5%) |
151 (17.6%) |
221 (12.3%) |
| 35+ |
76 (5.0%) |
249 (7.4%) |
84 (8.2%) |
140 (6.9%) |
71 (8.3%) |
110 (6.1%) |
| Unknown |
50 (3.3%) |
39 (1.2%) |
29 (2.8%) |
10 (0.5%) |
54 (6.3%) |
13 (0.7%) |
| Menopausal status | ||||||
| Premenopausal |
948 (61.8%) |
2,163 (64.1%) |
16 (1.6%) |
44 (2.2%) |
0 (0%) |
0 (0%) |
| Postmenopausal |
473 (30.9%) |
1,032 (30.6%) |
1,001 (98.0%) |
1,979 (97.4%) |
860 (100%) |
1794 (99.9%) |
| Unknown |
112 (7.3%) |
178 (5.3%) |
4 (0.4%) |
8 (0.4%) |
0 (0%) |
1 (0.1%) |
| Parity | ||||||
| Nulliparous |
294 (19.2%) |
638 (18.9%) |
130 (12.7%) |
249 (12.3%) |
114 (13.3%) |
235 (13.1%) |
| Parous |
1,145 (74.7%) |
2,652 (78.6%) |
824 (80.7%) |
1,686 (83.0%) |
674 (78.4%) |
1,428 (79.6%) |
| Unknown |
94 (6.1%) |
83 (2.5%) |
67 (6.6%) |
96 (4.7%) |
72 (8.4%) |
132 (7.4%) |
| Postmenopausal hormone therapya | ||||||
| Not current user |
158 (40.9%) |
411 (45.7%) |
404 (48.6%) |
1030 (58.6%) |
361 (57.8%) |
1,010 (69.1%) |
| Current, estrogen |
81 (21.0%) |
233 (25.9%) |
144 (17.3%) |
311 (17.7%) |
100 (16.0%) |
199 (13.6%) |
| Current, estrogen + progestin |
126 (32.6%) |
222 (24.7%) |
215 (25.9%) |
308 (17.5%) |
84 (13.4%) |
124 (8.5%) |
| Unknown |
21 (5.4%) |
34 (3.8%) |
68 (8.2%) |
108 (6.1%) |
80 (12.8%) |
129 (8.8%) |
| Family history | ||||||
| No |
1,207 (78.7%) |
2,970 (88.1%) |
777 (76.1%) |
1,719 (84.6%) |
627 (72.9%) |
1,450 (80.8%) |
| Yes |
256 (16.7%) |
384 (11.4%) |
210 (20.6%) |
292 (14.4%) |
190 (22.1%) |
332 (18.5%) |
| Unknown | 70 (4.6%) | 19 (0.6%) | 34 (3.3%) | 20 (1.0%) | 43 (5.0%) | 13 (0.7%) |
Data presented as mean (standard deviation) or n (%). aAmong postmenopausal women in the Mayo Mammography Health Study, the Nurses’ Health Study, the Nurses’ Health Study II, and the San Francisco Bay Area Breast Cancer SPORE and San Francisco Mammography Registry.