title: Occupational sedentariness and breast cancer risk.
abstract: BACKGROUND
  Epidemiological studies have indicated that physical activity reduces the risk of developing breast cancer. More recently, sedentary behavior has been suggested as a risk factor independent of physical activity level. The purpose of the present study was to investigate occupational sedentariness and breast cancer risk in pre- and postmenopausal women.
  
  
  METHODS
  In a population-based prospective cohort study (n = 29 524), working history was assessed by a questionnaire between 1990 and 1992. Participants were classified as having: (1) sedentary occupations only; (2) mixed occupations or (3) non-sedentary occupations only. The association between occupational sedentariness and breast cancer incidence was analyzed by Cox regression, adjusted for known risk factors and participation in competitive sports.
  
  
  RESULTS
  Women with a working history of occupational sedentariness had a significantly increased risk of breast cancer (adjusted HR 1.20; 95% CI 1.05, 1.37) compared with those with mixed or non-sedentary occupations. The association was stronger among women younger than 55 years (adjusted HR 1.54; 95% CI 1.20, 1.96), whereas no association was seen in women 55 years or older. Adjustment for participation in competitive sports did not change the association.
  
  
  CONCLUSIONS
  We found that occupational sedentariness was associated with increased breast cancer risk, especially in women younger than 55 years. This may be a modifiable risk factor by planning breaks during the working day. Whether this reduces the risk of breast cancer needs to be further studied.
authors.affiliation: a Department of Clinical Sciences and Cancer Epidemiology , Lund University , Lund , Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Johnsson
authors.affiliation: a Department of Clinical Sciences and Cancer Epidemiology , Lund University , Lund , Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Broberg
authors.affiliation: b Department of Clinical Sciences and Oncology , Lund University , Lund , Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Johnsson
authors.affiliation: c Department of Health Sciences , Lund University , Lund , Sweden.|d Lund University Diabetes Centre (LUDC), Genetic and Molecular Epidemiology (GAME) Unit, Clinical Research Centre , Skåne University Hospital , Lund , Sweden.
authors.forename: Åsa B
authors.initials: ÅB
authors.lastname: Tornberg
authors.affiliation: a Department of Clinical Sciences and Cancer Epidemiology , Lund University , Lund , Sweden.|b Department of Clinical Sciences and Oncology , Lund University , Lund , Sweden.
authors.forename: Håkan
authors.initials: H
authors.lastname: Olsson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D015444:Exercise; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009367:Neoplasm Staging; D016273:Occupational Exposure / Q000009:adverse effects*; D009790:Occupations / Q000706:statistics & numerical data*; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires