Breast cancer is the commonest cancer among females in Sri Lanka. Over the last 15 years, it has become a major public health concern, with its incidence rising from 6.8 to 20.6 per 100,000 women. It is shown that only 30% of the risk of breast cancer is explained by the commonly known risk factors related to reproductive life and family history. The greater hidden risk is imposed by its newer risk factors related to lifestyle, such as long-term physical inactivity.
To examine the risk of long-term physical inactivity on breast cancer among Sri Lankan women
A case-control study was conducted in Colombo, Sri Lanka during 2011-2012 among newly diagnosed cases of breast cancer (n=210) selected from the National Cancer Institute and unmatched controls excluded for breast cancer (n=206) selected from the breast clinic in the same hospital. Their lifetime physical activity level was assessed in relation to occupational, household and sports/recreational activities using the Lifetime Total Physical Activity Questionnaire (LTPAQ) validated for Sri Lankan women. Multivariable logistic regression analysis was carried out to identify the 'low level' of physical activity as a risk factor for breast cancer.
The median activity level for cases and controls was 130.5 MET-hours per week per year. Compared to the highest quartile (>169.3 MET-hours/week per year), women in the lowest quartile (<85.6 MET-hours/week per year) of lifetime total physical activity, showed a significant risk for breast cancer (adjusted OR=2.1 (95% CI: 1.2, 3.7; p= 0.008). By type of activity, the risk was decreased for occupational (OR = 0.53, 95% CI: 0.34, 0.83) and sports/recreational (OR = 0.62, 95% CI: 0.38, 1.00) activity, when comparing the highest and lowest quartiles.
This study provides evidence that high level of lifetime physical activity is associated with reduced breast cancer risk.