Is westernisation of lifestyle in South Africa affecting cancer risk?

18 November 2015 | Cancer prevention, Cancer research

Dr Sabina Rinaldi works as part of the Nutrition and Metabolism Section, Biomarkers Group at the International Agency for Research on Cancer. She has been awarded two research grants as part of World Cancer Research Fund International's Regular Grant Programme.  

World Cancer Research Fund International’s Continuous Update Project has found strong evidence that lifestyle factors affect breast cancer risk. Alcoholic drinks are linked to an increased risk of breast cancer at all ages. Meanwhile, being overweight increases the risk of postmenopausal breast cancer and physical activity is linked to a decreased risk. However, these associations are mainly based on studies focusing on Caucasian women, and there are indications that breast cancer may be different in women of African ethnicity. The rapid lifestyle changes that are occurring in Africa, make this an interesting population in terms of providing insights into the influence of diet, body fatness, physical activity and sedentary behaviour on breast cancer.

South Africa is becoming more urban

This is why South Africa - the richest of the Sub-Saharan African countries - is the ideal setting for our research into the impact of lifestyle changes on the breast cancer risk of African women. South Africa’s expanding urban areas are inhabited by a wide variety of people with contrasting behaviours, which make them good places to conduct epidemiological studies. South African women are also a useful cohort for our research as breast cancer is the most common cancer in this group, and studies have shown that there are large differences between the country’s urban and rural populations in terms of dietary habits, obesity, physical activity and sedentary behaviours.

For example, the prevalence of overweight and obesity is 61% among women living in urban areas and 48% among those living in rural locations. Body composition (percentage of lean vs fat tissue) may also operate differently in black and white women depending on where the fat is located in the body, and thus have different associations with breast cancer risk.

So with the support of World Cancer Research Fund UK, we have set up a study (the SABC study) at the Baragwanath Hospital in the Soweto area of Johannesburg to identify the causes of breast cancer in South African women. Women who have been diagnosed with breast cancer at the hospital are invited to participate in the study immediately after their diagnosis and before any therapy. Questionnaire data on lifestyle, reproductive factors, physical activity/inactivity, and diet are collected, along with height and weight measurements and blood and urine samples. To have a better estimate of their lean versus fat tissues, the women also undergo dual-energy X-ray absorptiometry and ultra sound imaging. To further understand why they developed breast cancer, their data is compared with that of healthy Soweto women who are of a similar age to the patients. So far more than 300 subjects have been recruited, and comparing the data from these two populations should shed light on the specific risk factors for breast cancer in African women living in Soweto.

In particular, the results of the SABC study will be key to identifying the risk factors associated with obesity, physical activity, and nutrition that may be modified to prevent or reduce the risk of the disease in the population. Preliminary results from the analysis of the information from first participants enrolled in the study will be presented at the AORTIC conference in Marrakech this week.

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Sabina Rinaldi | 18 November 2015

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