Body mass index change during adulthood and risk of oesophageal squamous-cell carcinoma in a Japanese population: the Japan Public Health (JPHC)-based prospective study

BACKGROUND: The influence of body mass index (BMI) change during adulthood on the development of oesophageal squamous-cell carcinoma (ESCC) is unknown. METHODS: Based on the Japan Public Health Center-based Prospective Study, we enrolled 103 238 participants from 1990 to 1994. Anthropometric data at age 20 years, baseline, and 5- and/or 10-year follow-up surveys were collected by questionnaire. The effect of BMI change between age 20 years and baseline on ESCC risk was estimated by Cox proportional hazards regression models. The updated BMI was taken into account by fitting a simple linear regression model for each individual, where the slope was incorporated into regressions as a time-varying variable. RESULTS: After excluding the first 5 years of observation, we identified 342 newly diagnosed ESCC cases. An increase in BMI during adulthood was linked with a decreased risk of ESCC development, with each 1% increase per 5 years corresponding to a 15% decrease in ESCC risk (95% confidence interval 9–21%). Identical estimates were obtained from time-dependent models. The importance of BMI change was not modified by gender, smoking, or alcohol drinking but confined to participants assessed as non-overweight at baseline. CONCLUSIONS: An increase in BMI during adulthood is associated with a lower risk of developing ESCC among non-overweight subjects.