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Smoking and colorectal cancer: A pooled analysis of 10 population‐based cohort studies in Japan
Author(s) -
Akter Shamima,
Islam Zobida,
Mizoue Tetsuya,
Sawada Norie,
Ihira Hikaru,
Tsugane Shoichiro,
Koyanagi Yuriko N.,
Ito Hidemi,
Wang Chaochen,
Tamakoshi Akiko,
Wada Keiko,
Nagata Chisato,
Tanaka Kenta,
Kitamura Yuri,
Utada Mai,
Ozasa Kotaro,
Sugawara Yumi,
Tsuji Ichiro,
Shimazu Taichi,
Matsuo Keitaro,
Naito Mariko,
Tanaka Keitaro,
Inoue Manami
Publication year - 2020
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.33248
Subject(s) - medicine , colorectal cancer , hazard ratio , proportional hazards model , cohort , cohort study , confidence interval , population , relative risk , cancer , smoking cessation , oncology , demography , environmental health , pathology , sociology
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.