Table 2.
Breast Cancer Reproductive and Hormonal Risk Factors by Level of Education in Ella Study Participants with Known Age at Diagnosis and Level of Education (n=1201)
| Participant characteristics | <High school (n=602) | High school (n=313) | >High school (n=286) |
|---|---|---|---|
| Age at diagnosis (years), mean±SD | 55.5±12.8 | 49.9±10.6 | 47.6±11.4 |
| Age at menarche (years), mean±SDa | 13.0±1.6 | 12.6±1.6 | 12.3±1.6 |
| Age at menarche <12 years, n (%)a | 92 (15.3) | 69 (22.0) | 90 (31.5) |
| Hormone contraceptive use (ever), n (%)b | 298 (49.5) | 195 (62.5) | 188 (66.0) |
| Nulliparity, n (%) | 44 (7.3) | 29 (9.3) | 46 (16.1) |
| Age at first full-term pregnancy, mean±SDc | 21.6±5.2 | 22.8±4.8 | 25.4±5.7 |
| Age at first full-term pregnancy ≥30 years, n (%)c | 53 (9.52) | 26 (9.15) | 56 (23.3) |
| Number of full-term pregnancies, mean±SD | 3.9±2.6 | 2.7±1.7 | 2.1±1.5 |
| Number of full-term pregnancies ≥3, n (%) | 444 (79.6) | 169 (59.5) | 111 (46.3) |
| Ever breastfed (if parous), n (%)d | 464 (83.8) | 198 (70.0) | 166 (69.5) |
| Lifetime breastfeeding (if parous, months), mean±SDd | 30.5±39.6 | 11.6±18.2 | 8.4±12.2 |
| Lifetime breastfeeding ≥6 months (if parous), n (%)d | 392 (70.8) | 143 (50.5) | 98 (41.0) |
| Time since last pregnancy (if premenopausal, years), mean±SDe | 14.6±8.1 | 12.9±7.0 | 11.3±7.6 |
| Time since last pregnancy ≤10 years (if premenopausal), n (%)e | 75 (34.6) | 55 (33.7) | 75 (48.7) |
| Postmenopausal, n (%)f | 356 (59.9) | 132 (43.0) | 96 (33.8) |
| Age at natural menopause (years), mean±SDg | 48.8±5.4 | 50.2±4.3 | 49.5±4.5 |
| Age at natural menopause ≥50 years, n (%)g | 142 (50.2) | 50 (56.8) | 27 (52.9) |
| Menopausal hormone therapy use, n (%)h | 62 (10.4) | 42 (13.6) | 55 (19.4) |
Missing data for age at menarche for 1 participant.
Missing data for hormone contraceptive use for 2 participants.
Missing data for age at first full-term pregnancy for 1 participant, plus 119 women were nulliparous.
Missing data for breastfeeding for 6 participants, plus 119 women were nulliparous.
Missing data for time since last pregnancy for 67 participants, plus 584 women were postmenopausal, and 16 women had unknown menopausal status.
Missing data for menopausal status for 16 participants.
Missing data for age at menopause for 162 participants who had non-natural (or unknown cause of) menopause, plus 601 women were premenopausal, and 16 women had unknown menopausal status.
Missing data for menopausal hormone therapy use for 12 participants.