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Sedentary work and the risk of breast cancer in premenopausal and postmenopausal women: a pooled analysis of two case–control studies
  1. Terry Boyle1,2,3,4,
  2. Lin Fritschi4,
  3. Lindsay C Kobayashi5,6,7,
  4. Jane S Heyworth8,
  5. Derrick G Lee1,2,
  6. Si Si4,
  7. Kristan J Aronson6,7,
  8. John J Spinelli1
  1. 1Cancer Control Research, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
  2. 2School of Population and Public Health, The University of British Columbia, Vancouver, British Columbia, Canada
  3. 3Centre for Medical Research, The University of Western Australia, Perth, Western Australia, Australia
  4. 4School of Public Health, Curtin University, Perth, Western Australia, Australia
  5. 5Department of Epidemiology and Public Health, University College London, London, UK
  6. 6Department of Public Health Sciences, Queen's University, Kingston, Ontario, Canada
  7. 7Division of Cancer Care and Epidemiology, Cancer Research Institute, Queen's University, Kingston, Ontario, Canada
  8. 8School of Population Health, The University of Western Australia, Perth, Western Australia, Australia
  1. Correspondence to Dr Terry Boyle, School of Public Health, Curtin University, GPO Box U1987, Perth, WA 6845 Australia; terry.boyle{at}curtin.edu.au

Abstract

Objectives There is limited research on the association between sedentary behaviour and breast cancer risk, particularly whether sedentary behaviour is differentially associated with premenopausal and postmenopausal breast cancer. We pooled data from 2 case–control studies from Australia and Canada to investigate this association.

Methods This pooled analysis included 1762 incident breast cancer cases and 2532 controls. Participants in both studies completed a lifetime occupational history and self-rated occupational physical activity level. A job-exposure matrix (JEM) was also applied to job titles to assess sedentary work. Logistic regression analyses (6 pooled and 12 study-specific) were conducted to estimate associations between both self-reported and JEM-assessed sedentary work and breast cancer risk among premenopausal and postmenopausal women.

Results No association was observed in the 6 pooled analyses, and 10 of the study-specific analyses also showed null results. 2 study-specific analyses provided inconsistent and contradictory results, with 1 showing statistically significant increased risk of breast cancer for self-reported sedentary work among premenopausal women cancer in the Canadian study, and the other a non-significant inverse association between JEM-assessed sedentary work and breast cancer risk among postmenopausal women in the Australian study.

Conclusions While a suggestion of increased risk was seen for premenopausal women in the Canadian study when using the self-reported measure, overall this pooled study does not provide evidence that sedentary work is associated with breast cancer risk.

  • sedentary work
  • breast cancer
  • job-exposure matrix

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