Cigarette smoking and risk of colorectal cancer among Norwegian women

Cancer Causes Control. 2009 Aug;20(6):895-903. doi: 10.1007/s10552-009-9327-x. Epub 2009 Mar 10.


Objective: The association between cigarette smoking and colorectal cancer (CRC) is still not established. In 2002, Norwegian women had the second highest incidence of CRC in the world. A large proportion of Norwegian women are ever smokers. We examined the association between cigarette smoking and CRC incidence among Norwegian women.

Methods: We followed 68,160 women, aged 30-69 years, from the Norwegian Women and Cancer Study who completed a questionnaire in 1996 or 1998 by linkages to national registers through 31 December 2005. Rate ratios (RRs) and 95% confidence intervals (CIs) were estimated by fitting Cox proportional hazard models. Subsequently, we estimated the population attributable fraction.

Results: Altogether, 425 incident cases of primary, invasive CRC were identified. Ever smokers had a 20% increased risk of CRC (RR = 1.2; 95% CI = 1.0-1.5), a 30% increased risk of colon (RR = 1.3; 95% CI = 1.0-1.7), and a 10% increased risk of rectal (RR = 1.1; 95% CI = 0.7-1.5) cancer compared to never smokers. The population attributable fraction was estimated to be 12% which indicated that approximately one in eight of the CRC cases could have been prevented at a population level.

Conclusion: Our results support the hypothesis that cigarette smoking is a preventable cause of CRC among women.

MeSH terms

  • Adult
  • Aged
  • Cohort Studies
  • Colorectal Neoplasms / etiology*
  • Colorectal Neoplasms / pathology*
  • Colorectal Neoplasms / prevention & control
  • Confidence Intervals
  • Data Collection
  • Female
  • Humans
  • Incidence
  • Middle Aged
  • Neoplasm Invasiveness / pathology
  • Norway / epidemiology
  • Population Surveillance*
  • Proportional Hazards Models
  • Prospective Studies
  • Registries
  • Risk Assessment
  • Risk Factors
  • Smoking / adverse effects*
  • Surveys and Questionnaires