title: Relationship between anthropometric factors, radiation exposure, and colon cancer incidence in the Life Span Study cohort of atomic bomb survivors.
abstract: OBJECTIVE
  We examined colon cancer risk in atomic bomb survivors to investigate whether excess body weight after the bombings alters sensitivity to radiation effects.
  
  
  METHODS
  Of the 56,064 Japanese atomic bomb survivors with follow-up through 2002 with self-reported anthropometric data obtained from periodic mail surveys, 1,142 were diagnosed with colon cancer. We evaluated the influence of body mass index (BMI) and height on radiation-associated colon cancer risk using Poisson regression.
  
  
  RESULTS
  We observed a similar linear dose-response relationship for the 56,064 subjects included in our analysis and the entire cohort of Japanese atomic bomb survivors [excess relative risk (ERR) per Gray (Gy) = 0.53, 95 % confidence interval (CI) 0.25-0.86]. Elevation in earliest reported BMI, BMI reported closest to colon cancer diagnosis, and time-varying BMI were associated with an elevated risk of colon cancer [relative risk (RR) per 5 kg/m(2) increase in BMI = 1.14, 95 % CI 1.03-1.26; RR = 1.16, 95 % CI 1.05-1.27; and RR = 1.15, 95 % CI 1.04-1.27, respectively]. Height was not significantly related to colon cancer risk. Inclusion of anthropometric variables in models had little impact on radiation risk estimates, and there was no evidence that sensitivity to the effect of radiation on colon cancer risk depended on BMI.
  
  
  CONCLUSIONS
  Radiation exposure and BMI are both risk factors for colon cancer. BMI at various times after exposure to the atomic bombings does not significantly influence the relationship between radiation dose and colon cancer risk, suggesting that BMI and radiation impact colon cancer risk independently of each other.
authors.affiliation: Department of Epidemiology, University of Washington, Health Sciences F-263, Seattle, WA 98195, USA. eob2@u.washington.edu
authors.forename: Erin O
authors.initials: EO
authors.lastname: Semmens
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Kopecky
authors.forename: Eric
authors.initials: E
authors.lastname: Grant
authors.forename: Robert W
authors.initials: RW
authors.lastname: Mathes
authors.forename: Nobuo
authors.initials: N
authors.lastname: Nishi
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sugiyama
authors.forename: Hiroko
authors.initials: H
authors.lastname: Moriwaki
authors.forename: Ritsu
authors.initials: R
authors.lastname: Sakata
authors.forename: Midori
authors.initials: M
authors.lastname: Soda
authors.forename: Fumiyoshi
authors.initials: F
authors.lastname: Kasagi
authors.forename: Michiko
authors.initials: M
authors.lastname: Yamada
authors.forename: Saeko
authors.initials: S
authors.lastname: Fujiwara
authors.forename: Masazumi
authors.initials: M
authors.lastname: Akahoshi
authors.forename: Scott
authors.initials: S
authors.lastname: Davis
authors.forename: Kazunori
authors.initials: K
authors.lastname: Kodama
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Li
mesh_terms: D017677:Age Distribution; D000886:Anthropometry; D001837:Body Weights and Measures / Q000706:statistics & numerical data*; D002277:Carcinoma / Q000453:epidemiology* / Q000209:etiology; D015331:Cohort Studies; D003110:Colonic Neoplasms / Q000453:epidemiology* / Q000209:etiology; D004781:Environmental Exposure / Q000009:adverse effects* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008136:Longevity / Q000502:physiology / Q000528:radiation effects; D008297:Male; D009381:Neoplasms, Radiation-Induced / Q000453:epidemiology*; D054043:Nuclear Weapons / Q000706:statistics & numerical data; D012307:Risk Factors; D017741:Survivors / Q000706:statistics & numerical data*