Table 1.
Distribution of select baseline characteristics among invasive breast cancer (BC) cases and non-cases included in the present analysis [ n (%)]
| Characteristics | Non-cases | BC cases |
|---|---|---|
| Total | 106,702 (100) | 5,676 (100) |
| Race/ethnicity | ||
| White | 91,831 (86.1) | 5,061 (89.2) |
| Black | 2,894 (2.7) | 134 (2.4) |
| Hispanic | 4,805 (4.5) | 153 (2.7) |
| Asian/Pacific Islander | 3,907 (3.7) | 193 (3.4) |
| Other/Mixed | 3,265 (3.1) | 135 (2.4) |
| Age group (years) | ||
| 20-29 | 5,212 (4.9) | 42 (0.7) |
| 30-39 | 14,906 (14.0) | 276 (4.9) |
| 40-49 | 28,880 (27.1) | 1,268 (22.3) |
| 50-59 | 25,562 (24.0) | 1,800 (31.7) |
| 60-69 | 16,655 (15.6) | 1,363 (24.0) |
| 70-79 | 10,807 (10.1) | 749 (13.2) |
| ≥80 | 4,680 (4.4) | 178 (3.1) |
| Family history of breast cancer (first degree relative) | ||
| Yes | 12,221 (11.5) | 965 (17.0) |
| No | 90,390 (84.7) | 4,504 (79.4) |
| Missing/Adopted | 4,091 (3.8) | 207 (3.7) |
| Age (years) at menarche | ||
| ≤11 | 23,558 (22.1) | 1,350 (23.8) |
| 12-13 | 59,732 (56.0) | 3,137 (55.3) |
| ≥14 | 21,746 (20.4) | 1,109 (19.5) |
| Missing/Never | 1,666 (1.6) | 80 (1.4) |
| Age (years) at first full-term pregnancy | ||
| ≤24 | 27,115 (25.4) | 1,522 (26.8) |
| 25-29 | 31,105 (29.2) | 1,753 (30.9) |
| ≥30 | 18,110 (17.0) | 987 (17.4) |
| Nulliparous* | 28,229 (26.5) | 1,310 (23.1) |
| Missing | 2,143 (2.0) | 104 (1.8) |
| Duration of breastfeeding (months) | ||
| Pregnant, no live births | 6,248 (5.9) | 272 (4.8) |
| Never | 16,977 (15.9) | 1,092 (19.2) |
| <6 | 18,615 (17.5) | 1,030 (18.2) |
| 6-11 | 14,378 (13.5) | 769 (13.6) |
| ≥12 | 25,978 (24.4) | 1,356 (23.9) |
| Nulliparous | 21,849 (20.5) | 1,036 (18.3) |
| Missing | 2,657 (2.5) | 121 (2.1) |
| BMI (mg/m 2 ) | ||
| <25 | 62,747 (58.8) | 3,123 (55.0) |
| 25-29 | 25,091 (23.5) | 1,517 (26.7) |
| ≥30 | 14,206 (13.3) | 794 (14.0) |
| Outlier/Unknown | 4,658 (4.4) | 242 (4.3) |
| Physical activity (hours/week) | ||
| ≤0.50 | 31,771 (29.8) | 2,028 (35.7) |
| 0.51-2.00 | 33,993 (31.9) | 1,801 (31.7) |
| 2.01-3.50 | 18,709 (17.5) | 876 (15.4) |
| 3.51-5.00 | 10,155 (9.5) | 482 (8.5) |
| >5.00 | 11,295 (10.6) | 438 (7.7) |
| Missing/Unknown | 779 (0.7) | 51 (0.9) |
| Menopausal status | ||
| Premenopausal | 44,158 (41.4) | 1,405 (24.8) |
| Perimenopausal | 2,140 (2.0) | 143 (2.5) |
| Postmenopausal | 51,819 (48.6) | 3,604 (63.5) |
| Missing | 8,585 (8.1) | 524 (9.2) |
| Hormone therapy use | ||
| Past/never | 18,796 (17.6) | 1,052 (18.5) |
| Current | 27,566 (25.8) | 2,204 (38.8) |
| Other (pre/peri) | 60,340 (56.6) | 2,420 (42.6) |
| Alcohol consumption (g/day) | ||
| None | 34,278 (32.1) | 1,663 (29.3) |
| <20 | 58,433 (54.8) | 3,139 (55.3) |
| ≥20 | 8,084 (7.6) | 594 (10.5) |
| Missing | 5,907 (5.5) | 280 (4.9) |
| Smoking status | ||
| Never | 71,010 (66.6) | 3,338 (58.8) |
| Former | 29,656 (27.8) | 1,938 (34.1) |
| Current | 5,349 (5.0) | 351 (6.2) |
| Missing | 687 (0.6) | 49 (0.9) |
| Total pack-years of smoking | ||
| Never smokers | 71,010 (66.6) | 3,338 (58.8) |
| ≤10 | 17,257 (16.2) | 988 (17.4) |
| 11-20 | 5,961 (5.6) | 416 (7.3) |
| 21-30 | 3,491 (3.3) | 280 (4.9) |
| ≥31 | 5,182 (4.9) | 417 (7.4) |
| Missing/Unknown | 3,801 (3.6) | 237 (4.2) |
| Moving status | ||
| Non-mover | 55,496 (52.0) | 3,496 (61.6) |
| Year of diagnosis | ||
| 1995-2001 | — | 2,384 (42.0) |
| 2002-2011 | — | 3,292 (58.0) |
| Tumor hormone responsive | ||
| Estrogen-receptor positive (ER+) | — | 4,293 (75.6) |
| Progesterone-receptor positive (PR+) | — | 3,477 (61.3) |
| ER+ or PR+ | — | 4,352 (76.7) |
| ER- and PR- | — | 704 (12.4) |
*Includes nulliparous women who were 1) pregnant without a live birth or 2) whose breast feeding history is unknown.