Smoking and risk of breast cancer in the Generations Study cohort

Breast Cancer Res. 2017 Nov 22;19(1):118. doi: 10.1186/s13058-017-0908-4.


Background: Plausible biological reasons exist regarding why smoking could affect breast cancer risk, but epidemiological evidence is inconsistent.

Methods: We used serial questionnaire information from the Generations Study cohort (United Kingdom) to estimate HRs for breast cancer in relation to smoking adjusted for potentially confounding factors, including alcohol intake.

Results: Among 102,927 women recruited 2003-2013, with an average of 7.7 years of follow-up, 1815 developed invasive breast cancer. The HR (reference group was never smokers) was 1.14 (95% CI 1.03-1.25; P = 0.010) for ever smokers, 1.24 (95% CI 1.08-1.43; P = 0.002) for starting smoking at ages < 17 years, and 1.23 (1.07-1.41; P = 0.004) for starting smoking 1-4 years after menarche. Breast cancer risk was not statistically associated with interval from initiation of smoking to first birth (P-trend = 0.97). Women with a family history of breast cancer (ever smoker vs never smoker HR 1.35; 95% CI 1.12-1.62; P = 0.002) had a significantly larger HR in relation to ever smokers (P for interaction = 0.039) than women without (ever smoker vs never smoker HR 1.07; 95% CI 0.96-1.20; P = 0.22). The interaction was prominent for age at starting smoking (P = 0.003) and starting smoking relative to age at menarche (P = 0.0001).

Conclusions: Smoking was associated with a modest but significantly increased risk of breast cancer, particularly among women who started smoking at adolescent or peri-menarcheal ages. The relative risk of breast cancer associated with smoking was greater for women with a family history of the disease.

Keywords: Breast neoplasms; Cohort studies; Smoking.

Publication types

  • Historical Article

MeSH terms

  • Adult
  • Biomarkers, Tumor
  • Breast Neoplasms / epidemiology*
  • Breast Neoplasms / etiology*
  • Breast Neoplasms / history
  • Cohort Studies
  • Female
  • History, 21st Century
  • Humans
  • Middle Aged
  • Population Surveillance
  • Risk Assessment
  • Risk Factors
  • Smoking / adverse effects*
  • Surveys and Questionnaires
  • United Kingdom / epidemiology


  • Biomarkers, Tumor