Table 3.

Multivariate-adjusted RR of breast cancer characterized by estrogen receptor status according to updated smoking exposure among women in the NHSII

Smoking variablesEstrogen receptor-positive breast cancer
Estrogen receptor-negative breast cancer
No. casesRR95% CIP for trendNo. casesRR95% CIP for trend
Never smokers3021.001521.00
    1–4 cigarettes/day (current)111.410.79–2.5210.220.03–1.16
    5–14 cigarettes/day (current)201.220.75–2.0091.140.58–2.24
    15–24 cigarettes/day (current)271.160.78–1.71141.300.75–2.27
    25+ cigarettes/day (current)100.810.43–1.530.571.410.65–3.30.4
Never smokers3021.001521.00
    1–4 cigarettes/day (past)411.461.05–2.03151.070.63–1.83
    5–14 cigarettes/day (past)561.551.16–2.07201.140.71–1.82
    15–24 cigarettes/day (past)380.980.69–1.40211.180.74–1.87
    25+ cigarettes/day (past)301.491.01–2.190.270.710.33–1.530.9
Duration of smoking
    Never smokers3021.001521.00
    <10 years281.170.78–1.75100.850.44–1.61
    10–14 years571.330.99–1.78301.400.94–2.08
    15–19 years571.260.94–1.70200.880.55–1.41
    20+ years951.371.07–1.740.003341.040.71–1.530.7
Age started smoking
    Never smokers (at baseline: 1989)3061.001531.00
    <15 years321.491.03–2.17141.190.69–2.08
    15–19 years1201.291.04–1.60420.900.63–1.27
    20+ years811.240.96–1.60371.280.89–1.85
Smoking duration before first pregnancy
    Never smokers3021.001521.00
    1–4 years211.050.65–1.6980.860.41–1.81
    5–9 years691.310.99–1.73271.100.72–1.69
    10–14 years701.471.11–1.93281.120.73–1.70
    15–19 years451.501.06–2.12191.270.76–2.13
    20+ years271.170.76–1.790.00370.690.31–1.520.8
  • Notes: Covariates: stratified by age and further adjusted for BMI, height, oral contraceptives, parity and age at first birth, age at menarche, family history of breast cancer, benign breast disease, alcohol consumption, and menopause status.