Association between shift work and the risk of death from biliary tract cancer in Japanese men.
BACKGROUND
There is increasing evidence suggesting that shift work involving night work may increase cancer risk.


METHODS
We examined the association between working rotating shifts and the risk of death from biliary tract cancer among Japanese men who participated in the Japan Collaborative Cohort Study. Of the 46,395 men recruited, 22,224 men aged 40-65 at baseline (1988-1990) who reported working full-time or were self-employed were included in the present analysis. The study subjects were followed through December 31, 2009. Information regarding occupation and lifestyle factors was collected using a self-administered questionnaire. Cox proportional hazard models were used to estimate the hazard ratio (HR) and 95 % confidence interval (CI) for the risk of death from biliary tract cancer in relation to shift work.


RESULTS
During a mean 17-year follow-up, we observed 94 biliary tract cancer deaths, including 23 deaths from gallbladder cancer and 71 deaths from extrahepatic bile duct cancer. Overall, shift work was associated with a statistically non-significant increase in the risk of biliary tract cancer, with an HR of 1.50 (95 % CI: 0.81-2.77), among rotating shift workers. When the analysis was limited to extrahepatic bile duct cancer, a significant association appeared, with a multivariable-adjusted HR of 1.93 (95 % CI: 1.00-3.72) for rotating shift workers.


CONCLUSIONS
Our data indicate that shift work may be associated with increased risk of death from extrahepatic bile duct cancer in this cohort of Japanese men. The association with gallbladder cancer remains unclear because of the small number of deaths.
Department of Public Health, Aichi Medical University School of Medicine, 1-1 Yazakokarimata, Nagakute, Aichi, 4980-1195, Japan. linys@aichi-med-u.ac.jp.
Yingsong
Y
Lin
Department of Public Health, Aichi Medical University School of Medicine, 1-1 Yazakokarimata, Nagakute, Aichi, 4980-1195, Japan. nishiyama@minos.ocn.ne.jp.
Takeshi
T
Nishiyama
Department of Epidemiology and Environmental Medicine, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421, Japan. mic@juntendo.ac.jp.
Michiko
M
Kurosawa
Department of Public Health, Hokkaido University Graduate School of Medicine, North 15, West 7, Kita-ku, Sapporo, 060-8638, Japan. tamaa@med.hokudai.ac.jp.
Akiko
A
Tamakoshi
Department of Preventive Medicine and Community Health, University of Occupational and Environmental Health, Japan, 1-1, Iseigaoka, Yahata-nishi-ku, 807-8555, Kitakyushu, Japan. kubo@med.uoeh-u.ac.jp.
Tatsuhiko
T
Kubo
Department of Preventive Medicine and Community Health, University of Occupational and Environmental Health, Japan, 1-1, Iseigaoka, Yahata-nishi-ku, 807-8555, Kitakyushu, Japan. zenq@med.uoeh-u.ac.jp.
Yoshihisa
Y
Fujino
Department of Public Health, Aichi Medical University School of Medicine, 1-1 Yazakokarimata, Nagakute, Aichi, 4980-1195, Japan. kikuchis@aichi-med-u.ac.jp.
Shogo
S
Kikuchi
D000328:Adult; D000368:Aged; D001661:Biliary Tract Neoplasms / Q000401:mortality* / Q000473:pathology; D003643:Death; D006801:Humans; D007564:Japan; D008019:Life Style; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D014940:Work Schedule Tolerance