PURPOSE: Although obesity is a risk factor for kidney cancer, few reports have investigated this association in Asian populations, notwithstanding the substantially different proportion of obesity between Asian and Western populations. Herein, we investigate the association between body mass index (BMI) and kidney cancer risk in Japanese persons, a relatively lean population. METHODS: The Japan Public Health Center-based Prospective Study was established in 1990 for Cohort I and in 1993 for Cohort II. Subjects in this study were 46,837 men and 52,625 women, 40-69 years of age, who answered a questionnaire at baseline and were followed up until the end of 2006. During this time, 101 men and 38 women were newly diagnosed with kidney cancer. RESULTS: In men, a U-shaped association between BMI and kidney cancer risk was observed, with a BMI of 23.0-24.9 showing the lowest risk (23-24.9: reference; <21: hazard ratio [HR] = 1.86; 95% confidence interval [CI] = 1.01-3.45, >or=27: HR = 1.99, 95% CI = 1.04-3.81). In women, the association was not clear because of the small number of cases, but high BMI was insignificantly associated with an increased risk of kidney cancer (21-24.9: reference; >or=25: HR = 1.55, 95% CI = 0.76-3.18). CONCLUSIONS: Not only high but also low BMI may increase risk of kidney cancer in populations with low average BMI. Copyright 2010 Elsevier Inc. All rights reserved.
PURPOSE: Although obesity is a risk factor for kidney cancer, few reports have investigated this association in Asian populations, notwithstanding the substantially different proportion of obesity between Asian and Western populations. Herein, we investigate the association between body mass index (BMI) and kidney cancer risk in Japanese persons, a relatively lean population. METHODS: The Japan Public Health Center-based Prospective Study was established in 1990 for Cohort I and in 1993 for Cohort II. Subjects in this study were 46,837 men and 52,625 women, 40-69 years of age, who answered a questionnaire at baseline and were followed up until the end of 2006. During this time, 101 men and 38 women were newly diagnosed with kidney cancer. RESULTS: In men, a U-shaped association between BMI and kidney cancer risk was observed, with a BMI of 23.0-24.9 showing the lowest risk (23-24.9: reference; <21: hazard ratio [HR] = 1.86; 95% confidence interval [CI] = 1.01-3.45, >or=27: HR = 1.99, 95% CI = 1.04-3.81). In women, the association was not clear because of the small number of cases, but high BMI was insignificantly associated with an increased risk of kidney cancer (21-24.9: reference; >or=25: HR = 1.55, 95% CI = 0.76-3.18). CONCLUSIONS: Not only high but also low BMI may increase risk of kidney cancer in populations with low average BMI. Copyright 2010 Elsevier Inc. All rights reserved.