Table 1.
Baseline characteristics and sex hormone levels of breast cancer case subjects and subcohort (Cont'd)
| Variable | Cases (n = 601) | Subcohort (n = 1,000) | Pa |
|---|---|---|---|
| Median BMI, kg/m2 (5th–95th percentile) | 27.6 (20.9–41.0) | 26.8 (20.4–39.6) | 0.03 |
| Missing (%) | 5 (1) | 20 (2) | |
| Alcohol consumption, n (%) | 0.03 | ||
| Abstainers | 242 (40) | 459 (46) | |
| <7 drinks/wk | 265 (44) | 423 (42) | |
| 7+ drinks/wk | 92 (15) | 116 (12) | |
| Missing | 2 (0) | 2 (0) | |
| Median physical activity, METs-h/wk (5th–95th percentile) | 8.8 (0–37.6) | 8.3 (0–41.2) | 0.68 |
| Missing (%) | 10 (2) | 13 (1) | |
| Median age, y (5th–95th percentile) | 67 (53–77) | 66 (53–77) | 0.20 |
| Race/ethnicity, n (%) | 0.15 | ||
| White | 517 (86) | 815 (82) | |
| Black | 50 (8) | 111 (11) | |
| Hispanic | 16 (3) | 35 (4) | |
| Asian/other | 17 (3) | 36 (4) | |
| Missing | 1 (0) | 3 (0) | |
| Highest education level, n (%) | 0.39 | ||
| High school or less | 129 (21) | 244 (24) | |
| College | 299 (50) | 472 (47) | |
| Postgraduate education | 162 (27) | 273 (27) | |
| Missing | 11 (2) | 11 (1) | |
| Marital status, n (%) | 0.11 | ||
| Never married | 37 (6) | 67 (6) | |
| Divorced/separated | 76 (13) | 168 (17) | |
| Widowed | 126 (21) | 214 (21) | |
| Married/marriage-like relationship | 356 (59) | 544 (55) | |
| Missing | 6 (1) | 7 (1) | |
| Smoking status, n (%) | 0.05 | ||
| Never | 311 (52) | 507 (51) | |
| Former | 259 (43) | 412 (41) | |
| Current | 24 (4) | 70 (7) | |
| Missing | 7 (1) | 11 (1) | |
| Age at menarche, n (%) | 0.23 | ||
| ≤10 y | 46 (8) | 80 (8) | |
| 11–12 y | 252 (42) | 379 (38) | |
| ≥ 13 y | 297 (49) | 538 (54) | |
| Missing | 6 (1) | 3 (0) | |
| Age at menopause, n (%) | 0.03 | ||
| ≤42 y | 66 (11) | 150 (15) | |
| 43–48 y | 124 (21) | 239 (24) | |
| 49–51 y | 144 (24) | 215 (22) | |
| ≥52 y | 220 (37) | 327 (32) | |
| Missing | 47 (8) | 69 (7) | |
| Parity, n (%) | 0.89 | ||
| 0 children | 90 (15) | 153 (15) | |
| 1–2 children | 192 (32) | 330 (33) | |
| ≥3 children | 312 (52) | 508 (51) | |
| Missing | 7 (1) | 9 (1) | |
| Age at first child's birth, n (%) | 0.18 | ||
| <20 y | 57 (9) | 100 (10) | |
| 20–24 y | 182 (30) | 348 (35) | |
| 25–29 y | 153 (25) | 211 (21) | |
| ≥30 y | 53 (9) | 76 (8) | |
| Nulliparous | 90 (15) | 153 (15) | |
| Missing | 66 (11) | 112 (11) | |
| First-degree relative with breast cancer, n (%) | 159 (26) | 220 (22) | 0.09 |
| Missing | 24 (4) | 69 (7) | |
| Median serum level of total estradiol, pg/mL | 10.9 (5.0–25.2) | 10.0 (4.3–24.2) | 0.01 |
| Median serum level of total insulin, µIU/mLb | 6.8 (2.5–18.1) | 5.6 (2.3–18.2) | 0.002 |
a
P value for comparison of cases with subcohort obtained from Wilcoxon signed rank-sum test (continuous data) and Pearson χ2 test (categorical data).
b
Among participants in study 1 (cases, n = 382; subcohort, n = 409).