Lifetime Occupational Physical Activity and the Risk of Breast Cancer: a Case-control Study

Objective: Epidemiological studies have shown that physical activity is a protective factor for breast cancer,although research findings are inconsistent regarding menopausal status. To determine the impact of occupationalphysical activity for breast cancer, a hospital-based case-control study was conducted in Poland in 2003-2007.
Methods: In total, data on physical activity of 858 invasive breast cancer cases and 1,085 controls were analyzed.Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression .Separate calculations were performed for premenopausal and postmenopausal women. Occupational physicalactivity was measured by sitting time and job titles. The risk estimates were controlled for potential risk factorsand lifetime household and recreational activities.
Results: A significantly decreased breast cancer risk wasfound among postmenopausal women declaring physically active jobs (requiring more than 80% of time spentstanding, walking) compared with those with low activity jobs (more than 80% of the working time spent in asitting position, during workhours) (OR=0.66; 95%CI 0.44-0.98, P trend=0.03). A similar inverse associationbetween occupational physical activity and breast cancer risk was also found when activity was evaluatedaccording to job titles provided by subjects. Postmenopausal women with physically demanding jobs, in particular,had a lower risk compared to those in sedentary occupations (OR=0.57; 95%CI 0.36-0.91, P trend=0.02).
Conclusion: These findings support observations from previous studies that sufficiently high occupational physicalactivity may reduce breast cancer risk, particularly among postmenopausal women.