Smoking and colorectal cancer: A pooled analysis of 10 population-based cohort studies in Japan

Shamima Akter, Zobida Islam, Tetsuya Mizoue, Norie Sawada, Hikaru Ihira, Shoichiro Tsugane, Yuriko N. Koyanagi, Hidemi Ito, Chaochen Wang, Akiko Tamakoshi, Keiko Wada, Chisato Nagata, Kenta Tanaka, Yuri Kitamura, Mai Utada, Kotaro Ozasa, Yumi Sugawara, Ichiro Tsuji, Taichi Shimazu, Keitaro MatsuoMariko Naito, Keitaro Tanaka, Manami Inoue

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


Smoking has been consistently associated with the risk of colorectal cancer (CRC) in Western populations; however, evidence is limited and inconsistent in Asian people. To assess the association of smoking status, smoking intensity and smoking cessation with colorectal risk in the Japanese population, we performed a pooled analysis of 10 population-based cohort studies. Study-specific hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox's proportional hazards model and then pooled using a random-effects model. Among 363 409 participants followed up for 2 666 004 person-years, 9232 incident CRCs were identified. In men, compared with never smokers, ever smokers showed higher risk of CRC. The HRs (95% CI) were 1.19 (1.10-1.29) for CRC, 1.19 (1.09-1.30) for colon cancer, 1.28 (1.13-1.46) for distal colon cancer and 1.21 (1.07-1.36) for rectal cancer. Smoking was associated with risk of CRC in a dose-response manner. In women, compared with never smokers, ever smokers showed increased risk of distal colon cancer (1.47 [1.19-1.82]). There was no evidence of a significant gender difference in the association of smoking and CRC risk. Our results confirm that smoking is associated with an increased risk of CRC, both overall and subsites, in Japanese men and distal colon cancer in Japanese women.

Original languageEnglish
Pages (from-to)654-664
Number of pages11
JournalInternational Journal of Cancer
Issue number3
Publication statusPublished - 2021 Feb 1


  • colorectal cancer
  • former smokers
  • pooled analysis
  • sites of colorectal cancer
  • smoking

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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