title: A follow-up study of physical activity and incidence of colorectal polyps in African-American women.
abstract: BACKGROUND
  Physical activity is associated with a reduced risk of colon cancer, but the effect of activity on colorectal adenomas, which are precursors to colon cancer, is uncertain. The influence of physical activity on colorectal adenomas among African-American women is of particular interest because African-American women have an increased risk of colon cancer relative to other U.S. women.
  
  
  METHODS
  We prospectively assessed the relation of physical activity to the incidence of colorectal polyps among African-American women. We followed 45,400 women in the Black Women's Health Study from 1997 to 2003. Data were obtained by biennial mailed questionnaires. During 287,029 person-years of follow-up, 1,390 women reported having been diagnosed with colorectal polyps. A review of medical records of 58 women who reported colorectal polyps indicated that 59% had adenomas and 41% had hyperplastic polyps. We converted hours per week of vigorous exercise and hours per week of walking to metabolic equivalent (MET)-hours. We estimated incidence rate ratios with Cox proportional hazard models, controlling for age, body mass index, smoking, family history of colorectal cancer, and education.
  
  
  RESULTS
  For total MET-hours/wk spent in walking and vigorous exercise, the incidence rate ratio decreased from 0.94 for <5 MET-hours/wk to 0.72 for >or=40 MET-hours/wk (P(trend) = 0.01). The inverse association was apparent among most subgroups examined, including women who may be at higher risk of colorectal adenomas because of being obese.
  
  
  CONCLUSIONS
  Increased physical activity is associated with a reduced incidence of colorectal polyps among African-American women.
authors.affiliation: Slone Epidemiology Center, Boston University, 1010 Commonwealth Avenue, Boston, MA 02215, USA. lrosenberg@slone.bu.edu
authors.forename: Lynn
authors.initials: L
authors.lastname: Rosenberg
authors.forename: Deborah
authors.initials: D
authors.lastname: Boggs
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Wise
authors.forename: Julie R
authors.initials: JR
authors.lastname: Palmer
authors.forename: Mark H
authors.initials: MH
authors.lastname: Roltsch
authors.forename: Kepher H
authors.initials: KH
authors.lastname: Makambi
authors.forename: Lucile L
authors.initials: LL
authors.lastname: Adams-Campbell
mesh_terms: D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data*; D000368:Aged; D003111:Colonic Polyps / Q000208:ethnology*; D015179:Colorectal Neoplasms / Q000208:ethnology*; D015444:Exercise; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D012307:Risk Factors