title: Lifetime recreational exercise activity and breast cancer risk among black women and white women.
abstract: BACKGROUND
  Physical inactivity is a potentially modifiable breast cancer risk factor. Because few data on this relationship exist for black women, we examined the relationship between breast cancer risk and lifetime and time- or age-specific measures of recreational exercise activity among white women and among black women.
  
  
  METHODS
  The Women's Contraceptive and Reproductive Experiences Study was a multicenter population-based case-control study of black women and white women aged 35-64 years with newly diagnosed invasive breast cancer. We collected detailed histories of lifetime recreational exercise activity during in-person interviews with 4538 case patients with breast cancer (1605 black and 2933 white) and 4649 control subjects (1646 black and 3033 white). Control subjects were frequency-matched to case patients on age, race, and study site. We examined associations between exercise activity measures (metabolic equivalents of energy expenditure [MET]-hours per week per year) and breast cancer risk overall and among subgroups defined by race, other breast cancer risk factors, and tumor characteristics by use of unconditional logistic regression. All statistical tests were two-sided.
  
  
  RESULTS
  Among all women, decreased breast cancer risk was associated with increased levels of lifetime exercise activity (e.g., average MET-hours per week per year, P(trend) = .002). An average annual lifetime exercise activity that was greater than the median level for active control subjects was associated with an approximately 20% lower risk of breast cancer, compared with that for inactivity (for 6.7-15.1 MET-hours/week/year, odds ratio [OR] = 0.82, 95% confidence interval [CI] = 0.71 to 0.93; for > or =15.2 MET-hours/week/year, OR = 0.80, 95% CI = 0.70 to 0.92). The inverse associations did not differ between black and white women (for MET-hours/week/year, P(trend) = .003 and P(trend) = .09, respectively; homogeneity of trends P = .16). No modification of risk was observed by disease stage, estrogen receptor status, or any breast cancer risk factor other than first-degree family history of breast cancer.
  
  
  CONCLUSIONS
  This study supports an inverse association between physical activity and breast cancer among black women and among white women.
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine, USC/Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA 90033, USA. lbern@usc.edu
authors.forename: Leslie
authors.initials: L
authors.lastname: Bernstein
authors.forename: Alpa V
authors.initials: AV
authors.lastname: Patel
authors.forename: Giske
authors.initials: G
authors.lastname: Ursin
authors.forename: Jane
authors.initials: J
authors.lastname: Sullivan-Halley
authors.forename: Michael F
authors.initials: MF
authors.lastname: Press
authors.forename: Dennis
authors.initials: D
authors.lastname: Deapen
authors.forename: Jesse A
authors.initials: JA
authors.lastname: Berlin
authors.forename: Janet R
authors.initials: JR
authors.lastname: Daling
authors.forename: Jill A
authors.initials: JA
authors.lastname: McDonald
authors.forename: Sandra A
authors.initials: SA
authors.lastname: Norman
authors.forename: Kathleen E
authors.initials: KE
authors.lastname: Malone
authors.forename: Brian L
authors.initials: BL
authors.lastname: Strom
authors.forename: Jonathan
authors.initials: J
authors.lastname: Liff
authors.forename: Suzanne G
authors.initials: SG
authors.lastname: Folger
authors.forename: Michael S
authors.initials: MS
authors.lastname: Simon
authors.forename: Ronald T
authors.initials: RT
authors.lastname: Burkman
authors.forename: Polly A
authors.initials: PA
authors.lastname: Marchbanks
authors.forename: Linda K
authors.initials: LK
authors.lastname: Weiss
authors.forename: Robert
authors.initials: R
authors.lastname: Spirtas
mesh_terms: D000293:Adolescent; D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data*; D001943:Breast Neoplasms / Q000737:chemistry / Q000453:epidemiology* / Q000235:genetics; D016022:Case-Control Studies; D002648:Child; D016001:Confidence Intervals; D015444:Exercise; D005260:Female; D006801:Humans; D015994:Incidence; D007899:Leisure Activities; D016015:Logistic Models; D008875:Middle Aged; D016017:Odds Ratio; D011960:Receptors, Estrogen / Q000032:analysis; D018570:Risk Assessment; D018426:SEER Program; D013997:Time Factors; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data*
chemical_list: D011960:Receptors, Estrogen