Multivariate RR estimates for breast cancer with 95% CI based upon 478 cases among women who have smoked for at least 20 years compared with never smokers within two (high/low) risk levels of breast cancer risk factors, Norwegian-Swedish Cohort Study, 1991-2000
| Confounding variables | Cases (n = 478) | Multivariate adjusted* (95% CI) | P† | |
|---|---|---|---|---|
| Age group at enrollment (y) | 30-44 | 253 | 1.25 (0.93-1.70) | 0.82 |
| 45-50 | 225 | 1.19 (0.86-1.65) | ||
| Age at menarche (y) | <13 | 145 | 0.93 (0.63-1.36) | 0.08 |
| 13+ | 333 | 1.42 (1.08-1.85) | ||
| Menopausal status‡ | Pre | 276 | 1.21 (0.91-1.61) | 0.74 |
| Post | 198 | 1.31 (0.92-1.88) | ||
| Parity | No | 65 | 1.18 (0.68-2.06) | 0.86 |
| Yes | 413 | 1.25 (0.98-1.58) | ||
| Age at first birth (y)§ | <25 | 255 | 1.31 (0.93-1.85) | 0.59 |
| 25+ | 158 | 1.15 (0.82-1.61) | ||
| Family history of breast cancer in the mother or sisters | No | 432 | 1.23 (0.97-1.55) | 0.82 |
| Yes | 46 | 1.35 (0.65-2.79) | ||
| Hormonal contraceptive use | Ever | 358 | 1.21 (0.93-1.56) | 0.76 |
| Never | 120 | 1.30 (0.86-1.96) | ||
| BMI | ≤23.9 | 328 | 1.30 (0.99-1.70) | 0.50 |
| >23.9 | 150 | 1.10 (0.75-1.62) | ||
| Consumption of alcohol | Nondrinkers | 82 | 1.43 (0.87-2.33) | 0.50 |
| Drinkers | 396 | 1.18 (0.92-1.51) |
↵* Adjusted for age at enrollment, menopausal status, number of children, age at first birth, hormonal contraceptive use, and consumption of alcohol where applicable.
↵† Test for heterogeneity between strata Wald χ2 statistics.
↵‡ Missing numbers due to equivocal menopausal status.
↵§ Among parous women.