Joint Effects of Smoking and Alcohol Drinking on Esophageal Cancer Mortality in Japanese Men: Findings from the Japan Collaborative Cohort Study

Background: The purpose of our study was to elucidate the joint effects of combined smoking and alcohol intake on esophageal cancer mortality in Japanese men through a large cohort study with a 20-year follow-up period. Materials and Methods: The Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study) was established in the late 1980s, including 46,395 men and 64,190 women aged 40 years and older and younger than 80. Follow-up of these participants was conducted until 2009. We used the Cox proportional hazards model to analyze data for 42,408 people excluding female participants, 411 people with histories of malignant neoplasms, and 3,576 with unclear smoking and drinking data. Results: The joint effects of age at start of smoking and amount of alcohol consumed per day were compared with non-smokers and non-drinkers or those consuming less than one unit of alcohol per day. The mortality risk was 9.33 (95% confidence interval, 2.55-34.2) for those who started smoking between ages 10 and 19 years and drinking at least three units of alcohol per day. Regarding the joint effects of cumulative amount of smoking and alcohol intake, the risk was high when both smoking and alcohol intake were above a certain level. Conclusions: In this Japanese cohort study, increased cancer mortality risks were observed, especially for people who both started smoking early and drank alcohol. Quitting smoking or not starting to smoke at any age and reducing alcohol consumption are important for preventing esophageal cancer in Japan.