Table 1.
Baseline characteristics for 70,575 women in the PLCO Cancer Screening Trial Cohort.
| Number | % | |
|---|---|---|
| Age at baseline | ||
| 55–59 | 24,381 | 34.6 |
| 60–64 | 21,405 | 30.3 |
| 65–69 | 15,405 | 21.8 |
| 70–74 | 9,384 | 13.3 |
| Race/ethnicity | ||
| White | 62,425 | 88.5 |
| African-American | 4,063 | 5.8 |
| Asian/Pacific Islander | 2,754 | 3.9 |
| Other* | 1,333 | 1.9 |
| Education | ||
| Less than H.S. | 4,598 | 6.5 |
| Completed H.S. | 28,588 | 40.5 |
| Beyond H.S. | 37,215 | 52.7 |
| Unknown | 174 | 0.3 |
| Marital status | ||
| Married or living as married | 48,749 | 69.1 |
| Widowed | 9,700 | 13.7 |
| Divorced or separated | 9,616 | 12.7 |
| Never married/missing | 2,510 | 4.5 |
| Mother or sister with breast cancer | ||
| No | 57,214 | 81.1 |
| Yes | 9,692 | 13.7 |
| Unknown | 3,669 | 5.2 |
| Age at menarche | ||
| < 12 | 14,259 | 20.2 |
| 12 – 13 | 37,816 | 53.6 |
| 14 – 15 | 15,105 | 21.4 |
| ≥ 16 | 3,208 | 4.6 |
| Missing | 187 | 0.3 |
| Years of oral contraceptive use | ||
| None | 32,170 | 45.6 |
| < 1 year | 10,219 | 14.5 |
| 2 – 3 years | 7,636 | 10.8 |
| 4 – 5 years | 5,208 | 7.4 |
| 6 – 9 years | 6,303 | 8.9 |
| ≥ 10 years | 8,830 | 12.5 |
| Missing | 209 | 0.3 |
| Parity and age at first birth | ||
| Nulliparous | 6,454 | 9.1 |
| 1–2 | ||
| < 20 years | 2,499 | 3.5 |
| 20–24 years | 9,336 | 13.2 |
| 25–29 years | 6,629 | 9.4 |
| 30–34 years | 2,405 | 3.4 |
| ≥ 35 years | 1,021 | 1.5 |
| 3–4 | ||
| < 20 years | 5,721 | 8.1 |
| 20–24 years | 16,227 | 23.0 |
| 25–29 years | 5,942 | 8.4 |
| 30–34 years | 1,020 | 1.5 |
| ≥ 35 years | 343 | 0.5 |
| ≥ 5 | ||
| < 20 years | 3,818 | 5.4 |
| 20–24 years | 7,162 | 10.2 |
| 25–29 years | 1,506 | 2.1 |
| 30–34 years | 193 | 0.3 |
| ≥ 35 years | 194 | 0.3 |
| Missing or unknown | 105 | 0.2 |
| Menopause Type | ||
| Natural | 43,572 | 61.7 |
| Surgical | 23,312 | 3233.0 |
| Radiation or medications | 2,346 | 3.3 |
| Missing | 1345 | 41.9 |
| Age at Natural Menopause | ||
| < 45 years | 4,468 | 6.3 |
| 45–49 years | 11,175 | 15.8 |
| 50–54 years | 22,134 | 31.4 |
| 55+ years | 5,709 | 8.1 |
| Missing | 86 | 0.1 |
| Menopausal hormone therapy use | ||
| None | 23,262 | 33.0 |
| Former use | 11,435 | 16.2 |
| Current use, ≤ 5 years | 11,546 | 16.4 |
| Current use, > 5 years | 23,712 | 33.6 |
| Missing | 620 | 0.9 |
| Body Mass Index (BMI; kg/m2) | ||
| < 18.5 | 892 | 1.3 |
| 18.5 – 24.9 | 27,251 | 38.6 |
| 25 – 29 | 24,214 | 34.3 |
| 30 – 34.9 | 11,102 | 15.7 |
| ≥ 35 | 6,297 | 8.9 |
| Missing | 819 | 1.2 |
*Other race/ethnicity includes Hispanic, American Indian, and missing/unknown.