Table 1.
Characteristics of women from the Women’s Health Initiative Study, 1993–2016 (N = 131,833)
| Breast cancer | ||
|---|---|---|
| Yes (n = 8,168) | No (n = 123,665) | |
| Age at entry [yrs.; median (IQR)] | 63 (57–69) | 63 (57–68) |
| Ethnicity: n (%) | ||
| White (not of Hispanic origin) | 7228 (88.5) | 102,870 (83.2) |
| Black or African-American | 480 (5.9) | 10,394 (8.4) |
| Other | 444 (5.4) | 10,091 (8.2) |
| Missing | 16 (0.2) | 310 (0.3) |
| Height [cm; median (IQR)] | 162.6 (158.4–166.6) | 161.8 (157.5–166.0) |
| Education: n (%) | ||
| High school or less | 3,703 (43.6) | 48,693 (39.4) |
| Postsecondary/some college | 2,943 (36.1) | 46,381 (37.5) |
| Graduate school/some graduate school | 1,463 (17.9) | 27,656 (22.4) |
| Missing | 59 (0.7) | 935 (0.8) |
| Family history of breast cancer in first-degree relative: n (%) | 1,864 (22.8) | 20,926 (16.9) |
| Age at menarche (y): n (%) | ||
| <12 | 1,894 (23.2) | 26,887 (21.7) |
| 12–13 | 4,538 (55.6) | 67,732 (54.8) |
| ≥14 | 1,704 (20.9) | 28,546 (23.1) |
| Missing | 32 (0.4) | 500 (0.4) |
| Parity: n (%) | ||
| Never been pregnant/no term pregnancy | 1,107 (13.6) | 14,523 (11.7) |
| 1 | 714 (8.7) | 10,760 (8.7) |
| 2 | 2,129 (26.1) | 30,744 (24.9) |
| 3 | 1,974 (24.2) | 29,681 (24.0) |
| 4+ | 2,191 (26.8) | 37,145 (30.0) |
| Missing | 53 (0.7) | 812 (0.7) |
| Breastfed: n (%) | 4,172 (51.1) | 62,962 (50.9) |
| Age at menopause (y): n (%) | ||
| <45 | 1,642 (20.1) | 29,469 (23.8) |
| 45–54 | 4,749 (58.1) | 69,103 (55.9) |
| ≥55 | 1,059 (13.0) | 13,286 (10.7) |
| Missing | 718 (8.8) | 11,807 (9.6) |
| Ever had mammogram: n (%) | 8,041 (98.5) | 120,831 (97.7) |
| HT use: n (%) | ||
| Never | 3,166 (38.8) | 53,770 (43.5) |
| Past | 1,128 (13.8) | 19,517 (15.8) |
| Current | 3,866 (47.3) | 50,268 (40.7) |
| Missing | 8 (0.1) | 110 (0.1) |
| Oral contraceptive: n (%) | 3,537 (43.3) | 50,904 (41.2) |
| History of benign breast disease: n (%) | 2,171 (26.6) | 25,243 (20.4) |
| Nonalcohol energy intake [kcal/dy; median (IQR)] | 1,508.1 (1,170.5–1,918.8) | 1,480.0 (1,137.5–1,903.45) |
| HLI score [median (IQR)] | 9 (12–14) | 10 (12–14) |
| Diet score [units; median (IQR)] | 26 (22–32) | 26 (21–32) |
| Alcohol [g/dy; median (IQR)] | 1.4 (0.0–7.4) | 1.0 (0.0–6.5) |
| Physical activity [Met-hours/week; median (IQR)] | 9.0 (2.5–18.0) | 8.8 (2.5–18.5) |
| BMI [kg/m2; median (IQR)] | 27.0 (23.8–31.2) | 26.7 (23.6–30.8) |
| Smoking status: n (%) | ||
| Never | 3,884 (47.6) | 62,219 (50.3) |
| Ex-smokers quit ≥10 y | 3,114 (38.1) | 42,860 (34.7) |
| Ex-smokers quit <10 y | 549 (6.7) | 8,376 (6.8) |
| Current ≤ 15 cigs/day | 39 (0.5) | 728 (0.6) |
| Current > 15 cigs/day | 479 (5.9) | 7,857 (6.4) |
| Missing | 103 (1.3) | 1,625 (1.3) |
Abbreviations: IQR, interquartile range; Met, metabolic equivalent.