Body mass index and subsequent risk of kidney cancer: a prospective cohort study in Japan.
OBJECTIVE
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.
Sawada
Norie
N
Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan. nsawada@ncc.go.jp
Inoue
Manami
M
Sasazuki
Shizuka
S
Iwasaki
Motoki
M
Yamaji
Taiki
T
Shimazu
Taichi
T
Tsugane
Shoichiro
S
D000328:Adult; D000368:Aged; D015992:Body Mass Index; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D007680:Kidney Neoplasms / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires