Table 2.
Associations between infertility and breast cancer incidence
| Cancer cases | Person-years | Age-adjusted | Multivariablea | |||
|---|---|---|---|---|---|---|
| HR (95% CI) | p value | HR (95% CI) | p value | |||
| Infertility | ||||||
| No infertility | 51,575 | 64,702,934 | 1.00 (reference) | . | 1.00 (reference) | . |
| Infertility | 2112 | 1,759,886 | 1.05 (1.00–1.10) | 0.029 | 0.96 (0.92–1.01) | 0.111 |
| Infertility and related diagnoses | ||||||
| No diagnosis | 49,822 | 63,500,014 | 1.00 (reference) | . | 1.00 (reference) | . |
| Ovulatory disturbances | 330 | 374,986 | 0.97 (0.87–1.08) | 0.589 | 0.94 (0.84–1.05) | 0.274 |
| Endometriosis | 1423 | 827,934 | 1.01 (0.95–1.06) | 0.845 | 1.02 (0.96–1.07) | 0.569 |
| Infertility | 1733 | 1,404,738 | 1.06 (1.01–1.11) | 0.024 | 0.98 (0.93–1.02) | 0.309 |
| Infertility and ovulatory disturbances | 114 | 153,635 | 0.99 (0.82–1.18) | 0.874 | 0.89 (0.74–1.07) | 0.206 |
| Infertility and endometriosis | 265 | 201,513 | 1.03 (0.92–1.17) | 0.592 | 0.93 (0.83–1.06) | 0.275 |
p < 0.05 is significant in all analyses. The dots represent the reference category
aAdjusted for age, calendar time, education level, country of birth, parity and age at first birth, salpingectomy, hysterectomy and bilateral oophorectomy