Table 2.
Reproductive Factors and Breast Cancer Cases (Pregnancy Associated, and Non-pregnancy Associated) and Healthy Controls, Nigeria, 1998-2011a
| Characteristic | PABC cases (≤2 years postpartum) N=152 |
Controls ≤2 years postpartum N=282 |
PABC cases (3-5 years postpartum) N=145 |
Controls with 3-5 years postpartum N=188 |
Non-PABC Cases N=421 |
Controls >5 years postpartum N=525 |
P c |
|---|---|---|---|---|---|---|---|
| Age at menarche (years) | |||||||
| 10-14 | 44 (29.7) | 100 (35.8) | 61 (43.0) | 72 (39.3) | 164 (41.5) | 204 (39.8) | |
| 15-16 | 72 (48.7) | 109 (39.1) | 64 (45.1) | 69 (37.7) | 155 (39.2) | 188 (36.7) | |
| 17-18 | 27 (18.2) | 49 (17.6) | 11 (7.8) | 32 (17.5) | 67 (17.0) | 96 (18.8) | |
| ≥19 | 5 (3.4) | 21 (7.5) | 6 (4.2) | 10 (5.5) | 9 (2.3) | 24 (4.7) | |
| mean ± SD | 15.2 ±1.8 | 15.2 ± 2.1 | 14.7 ±1.9 | 15.0 ± 2.2 | 14.9 ±2.0 | 15.1 ± 2.1 | 0.08 |
| Parity | |||||||
| 0 | 1 (0.7) d | 0 (0) | 0 (0) | 0 (0) | 93 (22.3) | 170 (32.4) | |
| 1-2 | 48 (31.6) | 129 (45.7) | 31 (21.4) | 65 (34.6) | 76 (18.2) | 77 (14.7) | |
| 3-5 | 86 (56.6) | 137 (48.6) | 89 (61.4) | 101 (53.7) | 182 (43.5) | 224 (42.7) | |
| ≥6 | 17 (11.2) | 16 (5.7) | 25 (17.2) | 22 (1.7) | 67 (16.0) | 54 (10.3) | |
| mean ± SD b | 3.4±1.7 | 2.9 ± 1.5 | 3.9±1.7 | 3.4 ± 1.7 | 4.1±2.1 | 2.6 ± 2.2 | <0.0001 |
| Age at first live birth (years) | |||||||
| Nulliparous | 1 (0.7) d | 0 (0) | 0 (0) | 0 (0) | 64 (16.5) | 129 (26.7) | |
| <25 | 58 (38.2) | 104 (36.9) | 77 (53.1) | 94 (50.0) | 236 (60.8) | 237 (49.1) | |
| 25-29 | 64 (42.1) | 123 (43.6) | 47 (32.4) | 73 (38.8) | 71 (18.3) | 95 (19.7) | |
| ≥30 | 29 (19.1) | 55 (19.5) | 21 (14.5) | 21 (11.2) | 17 (4.4) | 22 (4.6) | |
| mean ± SD | 25.9 ±4.6 | 26.1 ± 4.4 | 24.5 ±5.0 | 24.7 ± 4.5 | 21.9 ±4.6 | 22.9 ± 4.0 | <0.0001 |
| Lifetime duration of breastfeeding (months) b | |||||||
| ≤24 | 35 (23.8) | 95 (33.9) | 21 (14.5) | 37 (19.9) | 76 (23.4) | 238 (45.4) | |
| 25-48 | 56 (38.1) | 100 (35.7) | 48 (33.1) | 64 (34.4) | 74 (22.8) | 93 (17.8) | |
| 49-72 | 34 (23.1) | 65 (23.2) | 43 (29.7) | 57 (30.7) | 88 (27.1) | 119 (22.7) | |
| 73-96 | 13 (8.8) | 15 (5.4) | 21 (14.5) | 17 (9.1) | 48 (14.8) | 43 (8.2) | |
| >96 | 9 (6.1) | 5 (1.8) | 12 (8.3) | 11 (5.9) | 39 (12.0) | 31 (5.9) | |
| mean ± SD | 47.8 ±31.0 | 38.2 ± 24.3 | 55.7 ±32.2 | 50.0 ± 31.3 | 45.0 ±41.8 | 36.1 ± 35.0 | <0.0001 |
| Mean duration of breastfeeding per live birth (months) b | |||||||
| <12 | 50 (35.0) | 92 (35.1) | 36 (26.3) | 40 (23.4) | 107 (35.0) | 278 (55.2) | <0.001 |
| ≥12 | 93 (65.0) | 170 (64.9) | 101 (73.7) | 131 (76.6) | 199 (65.0) | 226 (44.8) | |
| Number of abortion | |||||||
| 0 | 106 (69.7) | 207 (73.4) | 110 (75.9) | 128 (68.1) | 269 (64.7) | 362 (69.8) | |
| 1 | 26 (17.2) | 39 (13.8) | 20 (13.8) | 27 (14.4) | 72 (17.3) | 77 (14.8) | |
| ≥2 | 20 (13.2) | 36 (12.8) | 15 (10.3) | 33 (17.6) | 75 (18.0) | 80 (15.4) | |
| mean ± SD | 0.5 ± 0.9 | 0.5 ± 1.0 | 0.4 ± 0.9 | 0.6 ± 0.9 | 0.6 ±1.0 | 0.6 ± 1.0 | 0.2 |
a
Among premenopausal women 21-50 years old (N=1,715)
b
Among parous premenopausal women 21-50 years old (N=1,446)
c
ANOVA or Wilcoxon rank-sum tests for continuous variables; Chi-square test for the categorical variable
d
Currently pregnant with first baby while breast cancer was diagnosed