title: Weight change in adulthood and risk of postmenopausal breast cancer: the HUNT study of Norway.
abstract: BACKGROUND
  Adult weight gain is associated with increased risk of postmenopausal breast cancer. Most previous studies are limited by using recalled or self-reported data, and it is not known if age-specific weight changes are important for breast cancer risk.
  
  
  METHODS
  In a Norwegian cohort of 28,153 women (and 900 incident breast cancers) with longitudinal anthropometric measurements over up to 30 years, we studied both overall and age-related weight changes in adulthood and risk of postmenopausal breast cancer.
  
  
  RESULTS
  Overall, weight gain in adulthood was associated with increased breast cancer risk (hazard ratio (HR) per kg per year 1.31, 95% confidence interval (CI) 1.11-1.54). Weight gain before (HR per kg per year 1.38, 95% CI 1.09-1.75) or around menopause (1.69, 95% CI 1.32-2.16) was associated with increased risk, but there was no clear risk increase associated with later weight gain (HR per kg per year 0.92, 95% CI 0.73-1.18).
  
  
  CONCLUSIONS
  Weight gain in adulthood was associated with increased risk of breast cancer. Our results suggest that weight gain before and around menopausal age may be particularly important for breast cancer risk among postmenopausal women.
authors.affiliation: Department of Public Health, Norwegian University of Science and Technology, Trondheim, Norway. mirjam.alsaker@ntnu.no
authors.forename: M D K
authors.initials: MD
authors.lastname: Alsaker
authors.forename: I
authors.initials: I
authors.lastname: Janszky
authors.forename: S
authors.initials: S
authors.lastname: Opdahl
authors.forename: L J
authors.initials: LJ
authors.lastname: Vatten
authors.forename: P R
authors.initials: PR
authors.lastname: Romundstad
mesh_terms: D000328:Adult; D015992:Body Mass Index; D001835:Body Weight; D001943:Breast Neoplasms / Q000453:epidemiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D009765:Obesity; D017698:Postmenopause; D011446:Prospective Studies; D012306:Risk; D012307:Risk Factors; D015430:Weight Gain