Smoking and colorectal cancer in a non-Western population: a prospective cohort study in Japan

J Epidemiol. 2003 Nov;13(6):323-32. doi: 10.2188/jea.13.323.


Background: The risk of colorectal cancer in relation to smoking habits has been examined mostly in Caucasians, and evidence for other ethnic groups is still scarce.

Methods: Our data came from the Japan Collaborative Cohort (JACC) Study. From 1988 through 1990, 25,260 men and 34,619 women aged 40-79 years completed a questionnaire on cigarette smoking and other lifestyle factors. Hazard ratios (HR) were estimated by fitting proportional hazards models.

Results: During the mean follow-up of 7.6 years through December 1997, we documented 408 incident colon cancers and 204 rectal cancers. We found a non-significant increase in colon cancer risk in male current smokers compared with never smokers. The multivariate-adjusted hazard ratios were 1.07 (95% confidence interval [CI]: 0.72-1.59) for ex-smokers and 1.23 (95% CI: 0.85-1.78) for current smokers. We however failed to observe a clear dose-response relationship between smoking intensity or duration and colon cancer risk. The adjusted hazard ratio was 1.07 (95% CI: 0.71-1.61) even for 40+ years of smoking. Almost no increase in colon cancer risk was detected for female smokers, and male smokers were not at an enhanced risk of rectal cancer.

Conclusions: Cigarette smoking was not a strong risk factor for colorectal cancer even after a long-term exposure, although a weak association remains open to discussion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Distribution
  • Aged
  • Asian Continental Ancestry Group
  • Cohort Studies
  • Colorectal Neoplasms / epidemiology*
  • Comorbidity
  • Confidence Intervals
  • Female
  • Humans
  • Japan / epidemiology
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Prospective Studies
  • Risk Assessment
  • Risk Factors
  • Sex Distribution
  • Smoking / epidemiology*
  • Surveys and Questionnaires