title: Contribution of behavioral risk factors and obesity to socioeconomic differences in colorectal cancer incidence.
abstract: BACKGROUND
  Health behaviors are known risk factors for colorectal cancer and are more common in low socioeconomic status (SES) populations. We evaluated the extent to which behavioral risk factors and body mass index (BMI) explain SES disparities in colorectal cancer incidence, overall and by tumor location.
  
  
  METHODS
  We analyzed prospective National Institutes of Health-AARP Diet and Health Study data on 506 488 participants who were recruited in 1995-1996 from six US states and two metropolitan areas and followed through 2006. Detailed baseline data on risk factors for colorectal cancer, including health behaviors, were obtained using questionnaires. SES was measured by self-reported education and census-tract data. The outcome was primary incident invasive colorectal adenocarcinoma. Poisson regression was used to estimate the association between SES and risk of incident colorectal cancer, with adjustment for age, sex, race and ethnicity, family history, and state of residence. The model estimates were used to derive percentage mediation by behavioral risk factors; bias-corrected 95% confidence intervals were obtained through bootstrap techniques.
  
  
  RESULTS
  Seven-thousand six-hundred seventy-six participants developed colorectal cancer during follow-up. SES differences in prevalence of physical inactivity, unhealthy diet, smoking, and unhealthy weight each explained between 11.3% (BMI) and 21.6% (diet) of the association between education and risk of colorectal cancer and between 8.6% (smoking) and 15.3% (diet) of the association between neighborhood SES and risk of colorectal cancer. Health behaviors and BMI combined explained approximately 43.9% (95% CI = 35.1% to 57.9%) of the association of education and 36.2% (95% CI = 28.0% to 51.2%) of the association of neighborhood SES with risk of colorectal cancer. The percentage explained by all factors and BMI combined was largest for right colon cancers and smallest for rectal cancers.
  
  
  CONCLUSIONS
  A substantial proportion of the socioeconomic disparity in risk of new-onset colorectal cancer, and particularly of right colon cancers, may be attributable to the higher prevalence of adverse health behaviors in low-SES populations.
authors.affiliation: Department of Family Medicine and Community Health, University of Pennsylvania Perelman School of Medicine, 2 Gates, 3400 Spruce St, Philadelphia, PA 19104, USA. Chyke.Doubeni@uphs.upenn.edu
authors.forename: Chyke A
authors.initials: CA
authors.lastname: Doubeni
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Major
authors.forename: Adeyinka O
authors.initials: AO
authors.lastname: Laiyemo
authors.forename: Mario
authors.initials: M
authors.lastname: Schootman
authors.forename: Ann G
authors.initials: AG
authors.lastname: Zauber
authors.forename: Albert R
authors.initials: AR
authors.lastname: Hollenbeck
authors.forename: Rashmi
authors.initials: R
authors.lastname: Sinha
authors.forename: Jeroan
authors.initials: J
authors.lastname: Allison
mesh_terms: D000368:Aged; D015992:Body Mass Index; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000209:etiology; D015986:Confounding Factors, Epidemiologic; D005247:Feeding Behavior; D005260:Female; D005500:Follow-Up Studies; D015438:Health Behavior; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D012111:Residence Characteristics; D012307:Risk Factors; D012309:Risk-Taking; D057185:Sedentary Behavior; D012907:Smoking / Q000009:adverse effects; D012923:Social Class; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology