title: Influence of lifestyle factors on mammographic density in postmenopausal women.
abstract: BACKGROUND
  Mammographic density is a strong risk factor for breast cancer. Apart from hormone replacement therapy (HRT), little is known about lifestyle factors that influence breast density.
  
  
  METHODS
  We examined the effect of smoking, alcohol and physical activity on mammographic density in a population-based sample of postmenopausal women without breast cancer. Lifestyle factors were assessed by a questionnaire and percentage and area measures of mammographic density were measured using computer-assisted software. General linear models were used to assess the association between lifestyle factors and mammographic density and effect modification by body mass index (BMI) and HRT was studied.
  
  
  RESULTS
  Overall, alcohol intake was positively associated with percent mammographic density (P trend  = 0.07). This association was modified by HRT use (P interaction  = 0.06): increasing alcohol intake was associated with increasing percent density in current HRT users (P trend  = 0.01) but not in non-current users (P trend  = 0.82). A similar interaction between alcohol and HRT was found for the absolute dense area, with a positive association being present in current HRT users only (P interaction  = 0.04). No differences in mammographic density were observed across categories of smoking and physical activity, neither overall nor in stratified analyses by BMI and HRT use.
  
  
  CONCLUSIONS
  Increasing alcohol intake is associated with an increase in mammography density, whereas smoking and physical activity do not seem to influence density. The observed interaction between alcohol and HRT may pose an opportunity for HRT users to lower their mammographic density and breast cancer risk.
authors.affiliation: Institution of Medical Epidemiology and Biostatistics, Karolinska Institutet, Nobels Väg 12A, Stockholm, Sweden.
authors.forename: Judith S
authors.initials: JS
authors.lastname: Brand
authors.affiliation: Institution of Medical Epidemiology and Biostatistics, Karolinska Institutet, Nobels Väg 12A, Stockholm, Sweden.
authors.forename: Kamila
authors.initials: K
authors.lastname: Czene
authors.affiliation: Institution of Medical Epidemiology and Biostatistics, Karolinska Institutet, Nobels Väg 12A, Stockholm, Sweden.
authors.forename: Louise
authors.initials: L
authors.lastname: Eriksson
authors.affiliation: Institution of Medical Epidemiology and Biostatistics, Karolinska Institutet, Nobels Väg 12A, Stockholm, Sweden.
authors.forename: Thang
authors.initials: T
authors.lastname: Trinh
authors.affiliation: National Clinical Research Centre, Level 3, Dermatology Block, Hospital Kuala Lumpur, Jalan Pahang, Kuala Lumpur, Malaysia ; Julius Centre University of Malaya, Faculty of Medicine, University of Malaya, Lembah Pantai, Kuala Lumpur, Malaysia.
authors.forename: Nirmala
authors.initials: N
authors.lastname: Bhoo-Pathy
authors.affiliation: Institution of Medical Epidemiology and Biostatistics, Karolinska Institutet, Nobels Väg 12A, Stockholm, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Hall
authors.affiliation: Department of Clinical Science and Education, Södersjukhuset (KI SÖS), S1. Sjukhusbacken 10, Stockholm, Sweden.
authors.forename: Fuat
authors.initials: F
authors.lastname: Celebioglu
mesh_terms: D000368:Aged; D000428:Alcohol Drinking / Q000009:adverse effects*; D015992:Body Mass Index; D000071060:Breast Density; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000209:etiology*; D016022:Case-Control Studies; D005260:Female; D020249:Hormone Replacement Therapy / Q000009:adverse effects*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008019:Life Style; D016014:Linear Models; D042361:Mammary Glands, Human / Q000002:abnormalities*; D008327:Mammography; D008875:Middle Aged; D009043:Motor Activity; D017698:Postmenopause; D012307:Risk Factors; D012907:Smoking; D011795:Surveys and Questionnaires