Lung cancer mortality and body mass index in a Japanese cohort: Findings from the Japan Collaborative Cohort Study (JACC Study)

Objective: To determine the relationship of body mass index (BMI) and BMI changes during adulthood to lung cancer mortality in a large-sized Japanese cohort. Methods: We followed 29,350 men for a maximum of 11 years in the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study), which was initiated from 1988 to 1990. Complementary log-log modeling was employed with age, smoking status, and family history of lung cancer as covariates. Anthropometric measurements used were BMI at baseline, BMI around age 20, and adulthood BMI loss defined between the two measurements. Independent effects of these three measurements on lung cancer mortality were evaluated by applying the method of generalized estimation equations to the model for adjustment of intra-individual correlation. Results: Never smokers showed that high BMI both at baseline and around age 20 significantly predict lung cancer mortality (P < 0.05). Adulthood BMI loss significantly (P < 0.05) elevated the risk for lung cancer mortality among current smokers, implying their enhanced vulnerability to lung cancer risk among smokers. Conclusions: The risk for lung cancer mortality is elevated by a mechanism related to smoking-induced weight loss during adulthood.