Physical activity reduces breast cancer risk: a case-control study in Tunisia.Cancer Epidemiol 2011; 35(6):540-4CE
This study examined the relationship between lifetime history of physical activity and breast cancer risk.
The case-control study was conducted on 400 women with histological confirmed breast cancer operated during the 2006-2009 period at Farhat Hached University Hospital, Sousse, Tunisia, and 400 cancer-free controls, aged 25-75 years. The physical activity was assessed using a structured questionnaire on each activity: type, duration, frequency, and intensity. Odds ratios (ORs), 95% confidence intervals (CI) and a full confounding assessment, included in this analysis, were derived using logistic regression.
These cases had lower lifetime averages for total physical activity for both forms of activity measurements (hours/week/year and MET-hours/week/year) and (P(trend)<0.001 and P(trend)=0.002, respectively). Significant risk reductions were found in total physical activity for both forms of activity measurements (OR=0.27, 95% CI: 0.18-0.52, OR=0.42, 95% CI: 0.26-0.73, respectively) for the highest versus the lowest level of activity (P(trend)=0.001 and 0.004, respectively). The stratification by menopausal status showed a significant 56% reduction in breast cancer risk for post-menopausal women (P(trend)=0.001, adjusted for age). The risk was further reduced to 68% (P(trend)=0.002, multivariate adjusted). Among pre-menopausal women, the total physical activity was not significantly associated with reduced risk, ORs were 0.88 (95% CI: 0.40-1.99, age adjusted) and 0.43 (95% CI: 0.12-1.38, multivariate adjusted).
These data are in concordance with the majority of previous reports which involved physical inactivity as an important risk factor for breast cancer.