Table 2.
Active and passive smoking in relation to breast cancer incidence overall and by menopausal statusa
| Smoking status | All women | Premenopausal | Postmenopausal | ||||
|---|---|---|---|---|---|---|---|
| Cases | P-yrsb | IRR (95% CI) | Cases | IRR (95 % CI) | Cases | IRR (95 % CI) | |
| Never active or passive | 141 | 100,184 | 1.00 | 70 | 1.00 | 52 | 1.00 |
| Passive only | 630 | 298,822 | 1.18 (0.98–1.42) | 296 | 1.42 (1.09–1.85) | 251 | 0.92 (0.68–1.24) |
| Ever smoker | 606 | 251,171 | 1.08(0.89–1.31) | 192 | 1.21(0.90–1.62) | 327 | 0.86(0.63–1.16) |
| Former smoker | 405 | 151,751 | 1.10 (0.90–1.35) | 116 | 1.25 (0.92–1.71) | 229 | 0.84 (0.61–1.15) |
| Current smoker | 201 | 99,420 | 1.05 (0.83–1.31) | 76 | 1.14 (0.81–1.61) | 98 | 0.90 (0.63–1.28) |
a
IRRs adjusted for age, questionnaire cycle, BMI, years of education, family history of breast cancer, age at menarche, parity, age at first birth, oral contraceptive use, vigorous exercise, alcoholic beverage consumption, menopausal status, age at menopause, and menopausal female hormone use
b
Person-years